## CBSE - MCQ Question Banks (के. मा. शि. बो . -प्रश्नमाला )

Q. 1 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: A weak nuclear force is responsible for the formation of stable helium nuclei through nuclear fusion reaction.
Reason: A weak nuclear force acts between nucleons to form a stable helium nucleus.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

During hydrogen fusion, hydrogen nuclei or protons are smashed together to overcome columbic repulsive force. Strong nuclear force binds protons and neutrons in the nucleus to creates an unstable form of helium nucleus. After that the weak nuclear force acts inside of individual nucleons, to form a stable helium atom by radioactive decay process.

Q. 2 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: Rutherford through his scattering experiment cannot identify the neutron.
Reason: A stream of high energy radiation of neutral particles is scattered in Rutherford scattering experiment. Earlier, neutron was supposed to be gamma rays.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

James Chadwick studied the Rutherford’s scattering experiment and proposed the particles emitted in this experiment as neutron. He passed the same radiation though Berylliums and paraffin found that like gamma rays, these particles remain undeflected in magnetic field but unlike gamma rays neutrons do not eject electron from atom.

Q. 3 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: Technology cannot come before physics.
Reason: Technology is based on the results of the advanced discovery in physics, without scientific law and theories technology cannot be developed.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

Technology and physics, each one shares the development of the other. Technological tools and instruments made countless contributions for the discovery of scientific theories and laws. For example, the ancient humans developed technologies to survive in earth through different raw materials and tools. They didn't understand the science behind those things.

Q. 4 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: When conservative forces act on freely falling object, the mechanical energy remains conserved.
Reason: The potential energy and kinetic energy of the freely falling body remains constant.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

According to law of conservation of mechanical energy for conservative forces, the sum of kinetic and potential energies at any point remains constant throughout the motion. The change in potential energy is equal and opposite to the change in kinetic energy.

Q. 5 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: It is usually easier to add neutrons to an atom than to add protons.
Reason: Inside the nucleus of atom nuclear force acting between two protons is much weaker than electrostatic force.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

Two protons can attract as well as repel each other due to nuclear force. When protons are far apart, the electrostatic repulsive force dominates the nuclear force. It becomes very difficult to add protons to an atom.

Q. 6 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: In a chemical reaction, mass remains conserved.
Reason: In a chemical reaction the total mass of the products is same as the total mass of the reactants.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

In a chemical reaction mass and energy are not conserved separately, but are conserved as a single entity called mass-energy. According to Einstein's famous equation for relativity, E = mc2, mass can be transformed into energy and energy can be transformed into mass.

Q. 7 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: Thermodynamics is a branch of physics that deals with the molecular movement of the system of particles.
Reason: Thermodynamics is based on statistics can be applicable only for the large number of molecules enclosed by a system.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

The thermodynamic approach is applicable on macroscopic level. It deals with the temperature of the system, while the kinetic theory and statistical mechanics are applicable at microscopically level to describe the molecular movement in term of the average kinetic energy of its molecules.

Q. 8 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: The properties of an ideal gas can be studied on either macroscopic or microscopic scale.
Reason: An ideal gas is composed of many randomly moving minute particles having no intermolecular attractive forces.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

On macroscopic scale, individual particles of a gas can be related using ideal gas equation while on microscopic scale, kinetic theory of gas is used to study the property of individual particles.

Q. 9 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: We use optical microscope in place of other measuring instruments to measure intermolecular distance.
Reason: The optical microscope uses visible light to look at the system under investigation.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

An optical microscope cannot resolve an object whose size is less than 6×10-7 m. We use electron microscope to measure intermolecular distance in which an accelerated beam of electrons is focused by properly designed electric and magnetic field.

Q. 10 Read the assertion and reason carefully to mark the correct option out of the options given below
Assertion: The dimensional correctness of a relation does not ensure its physical correctness.
Reason: The dimensional formula of some physical quantities like latent heat and gravitational potential is same.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

$\begin{array}{l}\text{Dimension of gravitational potential}\text{\hspace{0.17em}}\text{=}\text{\hspace{0.17em}}\frac{\text{Dimension}\text{\hspace{0.17em}}\text{of}\text{\hspace{0.17em}}\text{work}}{\text{Dimension}\text{\hspace{0.17em}}\text{of}\text{\hspace{0.17em}}\text{mass}}\\ \text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{=}\text{\hspace{0.17em}}\frac{\left[{\text{ML}}^{\text{2}}{\text{T}}^{\text{-2}}\right]}{\left[\text{M}\right]}\text{=}\left[{\text{L}}^{\text{2}}{\text{T}}^{\text{-2}}\right]\\ \text{Dimension of latent heat}\text{\hspace{0.17em}}\text{=}\text{\hspace{0.17em}}\frac{\text{Dimension}\text{\hspace{0.17em}}\text{of}\text{\hspace{0.17em}}\text{heat}}{\text{Dimension}\text{\hspace{0.17em}}\text{of}\text{\hspace{0.17em}}\text{mass}}\\ \text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{=}\text{\hspace{0.17em}}\frac{\left[{\text{ML}}^{\text{2}}{\text{T}}^{\text{-2}}\right]}{\left[\text{M}\right]}\text{=}\left[{\text{L}}^{\text{2}}{\text{T}}^{\text{-2}}\right]\end{array}$

Q. 11 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: A 10 inch long piece of cloth was measured thrice by using a metre scale. The measured values are 9.2 inches, 9.5 inches, and 10.2 inches. Out of three measurements, the last measurement was more accurate in comparison to previous measurements.
Reason: It is much closer to the average value of the measurement.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

The value obtained from the last measurement is closer to the actual length of the cloth.

Q. 12 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: The number of significant figures in 0.023 is two and significant figures in 0.3200 is four.
Reason: Zeros are not significant.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

In a number less than one, zeros between the decimal point and non-zero digit are not significant. But zeros to the right of non-zero digit are significant.

Q. 13 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: The dimensional formula of surface tension is same as that of tension.
Reason: Tension is the pulling force acting along the length of the object while surface tension is the force acting on the free surface of the object.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

Tension is the force acting along the length of the solid object whereas surface tension is the tendency of the liquid and is equivalent to force per unit length for imaginary line drawn on free surface of liquid. So, dimensional formula for surface tension is [ML0T-2] and dimensional formula for tension is [MLT-2].

Q. 14  The dimensional formula for the coefficient of viscosity is

A.  [ML -1T –1].

B.  [ML -1T –3].

C.  ML -2T –2].

D.  ML 2T –2].

#### SOLUTION

Q. 15  Dimensional formula of power is

A.  [M 1L 2T –3].

B.  [M 2L 1T –2].

C.  [M 1L 2T –1].

D.  [M 1L 1T –2].

#### SOLUTION

Q. 16  [M 1L 1T –1] are the dimensions of

A. power.

B. momentum.

C. force.

D. couple.

#### SOLUTION

Momentum = mass  velocity Dimensional formula is [M][LT-1]

Q. 17  The unit of power is

A.  kilowatt.

B.  kilowatt-hour.

C.  dyne.

D.  joule.

#### SOLUTION

The unit of power is kilowatt.

Q. 18 Among the following, the derived unit is:

A. mass.

B. volume.

C. length.

D. time.

#### SOLUTION

Volume = Mass/density

Q. 19 The density of a cube is measured by measuring its mass and the length of its sides. If the maximum errors in the measurement of mass and length are 3% and 2% respectively, then the maximum error in the measurement of the density of cube is

A. 5%

B. 7%

C. 9%

D. 10%

#### SOLUTION

Q. 20 If the volume and surface area of a cube are numerically equal, then the volume of such cube is

A. 216 cubic unit

B. 1000 cubic unit

C. 2000 cubic unit

D. 3000 cubic unit

#### SOLUTION

Volume of a cube = a3 Surface area of a cube = 6a2 ∴6a2 = a3   ⇒ a = 6 unit ⇒ Volume of a cube = 216 cubic unit

Q. 21  In vernier calipers N divisions of vernier scale coincide with (N - 1) divisions of main scale in which length of a division is 1 mm. The least count of the instrument in cm is

A.  N

B.  N  - 1

C.  (1/10)N

D. (1/N) - 1

#### SOLUTION

Q. 22 Area of a circle of radius 3.458 cm, upto correct significant figures, is:

A. 37.57 cm2

B. 37.56 cm2

C. 37.566 cm2

D. 37.5664 cm2

#### SOLUTION

Q. 23 [ML-1T-2] stand for the dimensional formula of

A. surface tension.

B. gravitational constant.

C. viscosity.

D. stress.

#### SOLUTION

[ML-1T-2] stand for the dimensional formula of stress.[MT-2] is the dimensional formula of surface tension,[M-1L3T-2] that of gravitational constant and [ML-1T-1] that of coefficient of viscosity.

Q. 24

A. [ML-1T-3]

B. [L4]

C. [ML5T-2]

D. [ML-5]

#### SOLUTION

Q. 25 Whose dimension  is  [MLT-1] ?

A. Linear momentum.

B. Angular momentum.

C. Angular Velocity.

D. Angular acceleration.

#### SOLUTION

Linear momentum , p = m  v.
[P] = [M][LT-1] = [MLT-1].

Q. 26 In SI unit, one Pascal is equal to

A. 1 dyne/cm2.

B. 1 newton/metre2.

C. 1 newton/meter.

D. 1 newton meter.

#### SOLUTION

One Pascal is equal to 1 newton/metre2.

Q. 27 In S.I. system, the unit of pressure is

A. dynes/cm2 .

B. newton/m.

C. pascal.

D. bar.

#### SOLUTION

In S.I. system, the unit of pressure is Pascal.

Q. 28

A. 1.89%

B. 5.66%

C. 0.63%

D. 2.78%

#### SOLUTION

Q. 29 The mass of block of wood is 87.2 g and its volume is 25 cm3. Its density up to the correct significant figures is

A. 3.488 g / cm3

B. 3.5 g / cm3

C. 3.48 g / cm3

D. 3.4 g / cm3

#### SOLUTION

Q. 30 Dimensions of Stefan’s constant is:

A. [ML2T-2]

B. [ML2T-2K-4]

C. [MT-3K-4]

D. [MT-2L0]

#### SOLUTION

Q. 31 Dimensional formula for angular momentum is:

A. [T-1]

B. [MLT-1]

C. [ML2T-1]

D. [M0L0T0]

#### SOLUTION

Angular momentum = Iω = [ML2][T-1] = [ML2T-1]

Q. 32 The dimensional formula for kinetic energy is

A. [M2L2T].

B. [ML2T-2].

C. [M0L-1].

D. [ML2T].

#### SOLUTION

Q. 33 1 kg is equal to

A. 1.6  1027 a.m.u

B. 2.6  1027 a.m.u

C. 0.6  10-27 a.m.u

D. 0.6  1027 a.m.u

#### SOLUTION

Q. 34 The number of astronomical units in one meter is

A. 6.67  10-10 AU.

B. 3.67  10-12 AU.

C. 6.67  10-12 AU.

D. 6.67  1012 AU.

#### SOLUTION

Q. 35 The mass of a body that weighs 1 N at a place where g = 9.8 m/s2 is

A. 0.102 kg .

B. 10.20 kg.

C. 102.26 kg .

D. 201.2 kg.

#### SOLUTION

Q. 36 The dimension of potential energy is same as the dimension of .............................. .

A. force

B. power

C. latent heat

D. work done

#### SOLUTION

Dimension of work done = [ML2T-2].
Dimension of potential energy = [ML2T-2].

Q. 37 The shortest time interval measured indirectly so far is

A. 10-2 seconds.

B. 10-12 seconds.

C. 1022 seconds.

D. 10-22 seconds.

#### SOLUTION

The shortest time interval is the time taken by the light to cross a distance of nuclear size in nearly 10-22 seconds.

Q. 38 The shortest distance measured indirectly so far is

A. 10-15 m.

B. 1015 m.

C. 10-17 m.

D. 10-11 m.

#### SOLUTION

The shortest distance measured indirectly so far is radius of proton, which is nearly 10-15 m.

Q. 39 Wattsecond is the unit of

A. power.

B. energy.

C. energy intentsity.

D. potential.

#### SOLUTION

watt = joule/second .
SI unit of energy can be written as wattsecond.

Q. 40 The dimensions of mass per unit length is

A. [ML-1T]

B. [M2L-1T-1]

C. [ML-1]

D. [M-1L-1]

#### SOLUTION

mass/length = M/L = [ML-1]

Q. 41 If the magnitude of force 'F' experienced by a certain object moving with speed 'v' is given by
F=Kv2. Then, the dimensional fomula of K is

A. [MLT-2]

B. [LT-1]

C. [L-2T-2]

D. [ML-1]

#### SOLUTION

[F] = [MLT-2] ; [V]=[L1T-1]
Given, F= Kv2
So, [MLT-2] = K [LT-1]2 = K[L2T-2]
[K]=[ML-1]

Q. 42 The dimensions of a and b in the relation F = a + bx, where, F is the force and x is the distance are

A. a = [MLT-2] , b = [ML0T-2]

B. a = [MLT-2] , b = [MLT-2]

C. a = [M2LT-2] , b = [ML0T-2]

D. a = [MLT-2] , b = [M2L0T-2]

#### SOLUTION

F = a = [MLT-2] F/x = b= [ML0T-2]

Q. 43 The dimension of time in power is

A. 1.

B. -1.

C. 2.

D. -3.

#### SOLUTION

Power = Work/time = [ML2T-2]/[T]                                = [ML2T-3]

Q. 44 A physical quantity is measured and the result is expressed as n and u where, u is the unit and n is the numerical value. If the result is expressed in various units then

A. nu.

B. nu2.

C. nu1/2.

D. n1/u.

#### SOLUTION

The result of any physical quantity if expressed in various units then, it is n1/u.

Q. 45 1micron=......m.

A. 10-4

B. 10-7

C. 10-5

D. 10-6

#### SOLUTION

1micron = 10-6m. Level : knowledge.

Q. 46 A kg is larger than a milligram by

A. 106 times.

B. 103 times.

C. 10-2 times.

D. 10-6 times.

#### SOLUTION

As 1 kg=103 g and 1 mg =10-3 g,we have 1kg=106 mg.

Q. 47 1 light year is equal to

A. 9.12 102 m.

B. 8.24 105 m.

C. 9.46 1015 m.

D. 2.28 1010 m.

#### SOLUTION

1 light year is the distance  travelled by light in vacuum in one year.
Velocity of light in vacuum = 3  108 m/s.
1 year= (365  24  60  60) s. Distance = speed  time.
1 light year = [(3  108) m/s  (365  24  60  60) s]

Q. 48 The S.I. unit used to express the amount of substance is

A. atom.

B. molecule.

C. electrons.

D. mole.

#### SOLUTION

One mole is the amount of substance which contains as many elementary entities as there are atoms in 0.012 kg of carbon-12. A mole has Avagadro`s number of atoms or molecules of the pure substance being measured.

Q. 49 Bohr lived in-

A. Japan

B. France

C. India

D. Denmark

#### SOLUTION

Niels Bohr was born in Copenhagen, Denmark on 7th October 1885.

Q. 50 What is the range of nuclear force?

A. 10 Fermi

B. 12 Fermi

C. 15 Fermi

D. 16 Fermi

#### SOLUTION

Nuclear force have the shortest range. They operate upto distances of 10-14 m.  10-15 m = 1 fermi or 10-14 m = 10 fermi

Q. 51 Who said that light is an electromagnetic wave?

A. Newton

C. Maxwell

D. Glasgow

#### SOLUTION

James Clark Maxwell gave electromagnetic theory, which states that light propagates in the form of electromagnetic waves.

Q. 52 Neutron was discovered by

A. C.V. Raman

B. J.J. Thomson

C. Albert Einstein

#### SOLUTION

Q. 53 Who among the following won Nobel prize twice in physics?

A. Bardeen

B. Einstein

C. Heisenberg

#### SOLUTION

Bardeen won the Nobel prize in 1956 for the discovery of transistor effect and in 1972 for the development of theory of superconductors known as BCS theory.

Q. 54 The exchange particles for electromagnetic force are

A. gravitons

B. photons

C. gluons

D. weak bosons

#### SOLUTION

The exchange particles for various forces are mentioned below. 1. Gravitational force  - gravitons 2. Weak nuclear force - weak bosons 3. Electromagnetic force - photons 4. Strong nuclear force - gluons

Q. 55 Quantum model of hydrogen atom was discovered by

A. Newton

B. Yukawa

C. Bohr

D. J.J. Thomson

#### SOLUTION

Niels Bohr obtained the energy levels and spectral frequencies of the hydrogen atom in 1913.

Q. 56 Which is not a part of Classical Physics?

A. Mechanics

B. Optics

C. Thermodynamics

D. Relativity

#### SOLUTION

As classical physics deals with the particles with velocities much less than that of light, therefore it doesn't include the theory of relativity.

Q. 57 Which one of the following is incorrectly matched?

A. Lactometer - Milk

B. Thermometer - Temperature

C. Humidity - Calorimeter

D. Barometer - Pressure

#### SOLUTION

Humidity is measured by hygrometer whereas a calorimeter is used to measure heat capacity.

Q. 58 The mass of an electron is 9.11x 10-31 kg. How many electrons would make half kg?

A. 5.5x 1029

B. 1.2x 1022

C. 1.2x 1028

D. 1.4x 1029

#### SOLUTION

Mass of an electron = 9.11x 10-31 kg Total mass = ½ kg Number of electron = =5.5x1029

Q. 59 Who discovered the theory of nuclear force?

A. Kelvin

B. Coulomb

C. S.N. Bose

D. Hideki Yukawa

#### SOLUTION

Hideki' Yukawa made an attempt to explain the nature of nuclear forces in 1934.

Q. 60 Name the weakest force in nature-

A. Gravitational forces

B. Nuclear force

C. Electric force

D. Magnetic Force

#### SOLUTION

Force                                        Relative Strength Gravitational force                            1 Electromagnetic force                    1036 Nuclear force                                    1038

Q. 61 Which forces are considered in classical physics?

A. Nuclear forces and weak forces

B. weak forces and electromagnetic forces

C. gravitational forces and nuclear forces

D. gravitation forces and electromagnetic forces

#### SOLUTION

In classical physics, we confine ourselves to the study of particles with size more than 10-6 m, moving with velocities negligible with the speed of light. The size restriction excludes any appreciable effects of nuclear forces or weak forces. Therefore, we need to consider only the gravitational and electromagnetic forces.

Q. 62 The weakest force in nature is

A. strong nuclear force.

B. weak nuclear force.

C. gravitational force.

D. electromagnetic force.

#### SOLUTION

The relative strength of the four fundamental forces in nature are 1. Gravitational force = 1 2. Weak nuclear force = 1025 3. Electromagnetic force = 1036 4. Strong nuclear force = 1038

Q. 63 Photocell works on the principle of

A. photoelectric effect .

B. laws of thermodynamics.

C. supe conductivity.

D. Bernoulli's principle.

#### SOLUTION

Photocell works on the principle of photoelectric effect which states that electrons are emitted when light radiations (photons) of suitable frequency fall on a metal surface.

Q. 64 Electron was discovered by

A. J.J Thomson.

B. S.N Bose.

C. M.N Saha.

D. Edwin Hubble.

#### SOLUTION

Electron was discovered by J.J.Thompson in the year 1897 as the particle radiated from cathode rays.

Q. 65 The range of Gravitational force is

A. 10-6 m

B. Infinite

C. 10-15m

D. Very Short

#### SOLUTION

As gravitational force varies inversely as r2, so its range is infinite.

Q. 66 Gravitational forces are

A. central forces.

B. non-central forces.

C. strong forces.

D. repulsive forces.

#### SOLUTION

Gravitational forces are central forces as they act along the line joining the centres of the two bodies.

Q. 67 S. Chandrasekhar is associated with the discovery of

A. structure and evolution of stars.

B. scattering of light by molecules.

C. laws of electromagnetic induction.

D. principle of buoyancy.

#### SOLUTION

He was awarded Nobel Prize in Physics in 1983 for his studies on the physical processes important to the structure and evolution of stars.

Q. 68 Optics involves the study of various phenomena connected with

A. light.

B. magnetism.

C. electricity.

D. electronics.

#### SOLUTION

Optics is the branch of physics which deals with the study of nature, properties and various natural phenomena related to light.

Q. 69 Charges in motion produce

A. electric effects and a electric field gives rise to a force on a moving charge.

B. magnetic effects and a electric field gives rise to a force on a moving charge.

C. electric effects and a magnetic field gives rise to a force on a moving charge.

D. magnetic effects and a magnetic field gives rise to a force on a moving charge.

#### SOLUTION

Charges in motion ( or electric current ) produce magnetic effects and a magnetic field gives rise to a force on a moving charge (electric effects). Electric and magnetic effects are, in general, inseparable – hence the name electromagnetic force.

Q. 70 Gravitational force

A. exists by virtue of the masses of bodies.

B. exists between two bodies on the earth only.

C. does not exist between bodies in the space.

D. is not a universal law.

#### SOLUTION

The gravitational force is the force of mutual attraction between any two objects by virtue of their masses. It is an universal force. Every object experiences this force due to every other object in the universe.

Q. 71 Classical Physics deals mainly with

A. microscopic phenomena.

B. macroscopic phenomena.

C. both microscopic and macroscopic phenomena.

D. the movements of minute particles including electrons and protons.

#### SOLUTION

Classical Physics deals mainly with macroscopic phenomena and includes subjects like Mechanics, Electrodynamics, Optics and Thermodynamics.

Q. 72 Thermodynamics

A. deals with the motion of bodies as a whole while mechanics does not.

B. does not deal with the thermal properties of a system.

C. and mechanics deal with the motion of bodies as a whole.

D. does not deal with the motion of bodies as a whole.

#### SOLUTION

Thermodynamics does not deal with the motion of bodies as a whole. But it may explain the movement of constituent particles inside a body and their heat energy. On the other hand, mechanics deals with the motion of bodies as a whole.

Q. 73 The vibrant colours exhibited by thin films of soap bubbles are explained by

A. Electrodynamics

B. Optics

C. Thermodynamics

D. Mechanics

#### SOLUTION

Optics deals with the phenomena involving light. The vibrant colours exhibited by thin films of soap bubbles occur due to the interference of light rays. Therefore, it can be explained by Optics.

Q. 74 The propagation of radio waves in the ionosphere is dealt in

A. Electrodynamics.

B. Optics.

C. Thermodynamics.

D. Mechanics.

#### SOLUTION

Electrodynamics is the branch of physics that deals with electromagnetism or with electric and magnetic phenomena associated with charged and magnetic bodies. Radio waves are electromagnetic waves. So, the propagation of radio waves in the ionosphere is dealt in electrodynamics.

Q. 75 Terrestrial and nuclear phenomena are included in

A. microscopic and macroscopic domains respectively.

B. macroscopic and microscopic domains respectively.

C. macroscopic domain only.

D. microscopic domain only.

#### SOLUTION

There are two domains of interest: macroscopic and microscopic. The macroscopic domain includes phenomena at the laboratory, terrestrial and astronomical scales. The microscopic domain includes atomic, molecular and nuclear phenomena.

Q. 76 Two principal thrusts in physics are

A. unification and buoyancy.

B. unification and reductionism.

C. reductionism and buoyancy.

D. buoyancy and air pressure.

#### SOLUTION

There are two principal thrusts in physics used to understand the reasons and concepts behind the physical phenomena occurring in the nature. These two thrusts are - unification and reductionism.

Q. 77 Wave nature of light cannot explain the theory of

A. reflection.

B. refraction.

C. interference.

D. photoelectric effect.

#### SOLUTION

The wave picture of light failed to explain the photoelectric effect properly as photoelectric effect purely is based on the particle nature of light.

Q. 78 On examining the extensive data on planetary motion collected by Tycho Brahe, Kepler deduced that

A. the path of planetary motion is circular.

B. the path of planetary motion is helical.

C. the path of planetary motion is random.

D. the path of planetary motion is elliptical.

#### SOLUTION

When Johannes Kepler examined the extensive data on planetary motion collected by Tycho Brahe, he concluded that the planetary circular orbits in heliocentric theory (sun at the centre of the solar system) had to be replaced by elliptical orbits to fit the data better.

Q. 79 Gravitational forces

A. follow inverse square law .

B. are non-central forces.

C. are non-conserved forces.

D. do not exist between microscopic particles.

#### SOLUTION

Gravitational forces, F= Gm1m2/r2 where m1 and m2 are masses of two different bodies and r is the distance between the two. From this, we can conclude that gravitational forces follow inverse square law. Every object in the universe experiences this force due to every other object.

Q. 80 In heliocentric theory,

A. the earth is imagined to be at the centre.

B. all the planets and the sun are imagined to revolve around the earth and the earth is stationary.

C. all the planets are imagined to revolve around the earth and the earth is stationary.

D. the sun is imagined to be stationary and all the planets revolving around it.

#### SOLUTION

In heliocentric theory, the sun is imagined to be stationary and all the planets revolving around it. And geocentric theory imagines the earth to be at the centre of the universe.

Q. 81 The symmetry of nature with respect to translation (i.e. displacement) in time and space gives rise to the laws of conservation of

A. energy and linear momentum respectively.

B. energy and angular momentum respectively.

C. linear momentum and energy respectively.

D. angular momentum and energy respectively.

#### SOLUTION

If an experiment is carried out today and is repeated after two years under the same conditions, we will get the same result. And the laws of physics are applicable in any part of the universe. Hence, the symmetry of nature with respect to translation (i.e. displacement) in time and space gives rise to the laws of conservation of energy and momentum, respectively.

Q. 82 The law(s) of conservation that led to the prediction of the existence of a new particle now called neutrino

A. is law of conservation of energy.

B. is law of conservation of momentum.

C. is law of conservation of mass.

D. are laws of conservation of energy and momentum.

#### SOLUTION

In  -decay, the energy and momentum are not conserved without the consideration of a particle and its antiparticle called neutrino and antineutrino respectively. This led to the prediction of the existence of such particles.

Q. 83 The laws of conservation of total linear momentum and the total angular momentum are derived from Newton’s laws. So, these laws are valid

A. in microscopic domains.

B. in macroscopic domains.

C. in the domains where Newton’s laws are valid.

D. in all universal domains.

#### SOLUTION

Even though the laws of conservation of total linear momentum and the total angular momentum can be derived from Newton’s laws of motion in mechanics, but their validity goes beyond mechanics. They are the basic conservation laws of nature in all domains, even in those where Newton’s laws may not be valid.

Q. 84 The general law of conservation of energy or the first law of thermodynamics is true for

A. all conservative forces and for any kind of transformation between different forms of energy.

B. all non-conservative forces and for any kind of transformation between different forms of energy.

C. all conservative forces and for a few kinds of transformation between different forms of energy.

D. all forces and for any kind of transformation between different forms of energy.

#### SOLUTION

The general law of conservation of energy is true for all forces and for any kind of transformation between different forms of energy. The expressions for energy can be written for every physical system. When all forms of energy e.g., heat, mechanical energy, electrical energy etc., are counted, it turns out that energy is conserved. In short, the total energy of an isolated system is always conserved.

Q. 85 The conserved quantities of nature

A. should remain constant in time.

B. does not necessarily remain constant in time.

C. should remain constant for a particular period of time.

D. are total energy, total angular momentum and total linear momentum in isolated systems only.

#### SOLUTION

The conserved quantities of nature should remain constant in time. Besides, total energy, total angular momentum and total linear momentum, quantities like charge, mass, spin, etc are also conserved in isolated systems.

Q. 86 The range of weak nuclear force is of the order of

A. 10-16 m.

B. 10-15 m.

C. 10-14 m.

D. 10-12 m.

#### SOLUTION

The range of weak nuclear force is smaller than that of the strong nuclear force (10-15 m range). So, its range is of the order of 10-16 m.

Q. 87 The strong nuclear force is

A. charge dependent and of short range.

B. charge independent and of long range.

C. charge independent and of short range.

D. charge dependent and of long range.

#### SOLUTION

The strong nuclear force is charge-independent and acts equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron. Its range is, however, extremely small, of about nuclear dimensions (10–15m).

Q. 88 Strong nuclear force is

A. the weakest fundamental force.

B. the strongest fundamental force.

C. stronger than gravitational and weak forces but weaker than electromagnetic forces.

D. stronger than weak forces but weaker than gravitational and electromagnetic forces.

#### SOLUTION

The strong nuclear force is the strongest of all fundamental forces, about 100 times the electromagnetic force in strength.

Q. 89 Rocket propulsion is based on

A. isotropy of space.

B. homogeneity of space.

C. Newton`s third law of motion.

D. Bernoulli's principle.

#### SOLUTION

Action: The burnt fuel which appears in the form of hot and highly compressed gases escapes through the nozzle in backward direction. Reaction: The escaping gases push the rocket forward with the same force.

Q. 90 Nuclear forces are

A. short range forces.

B. long range forces.

C. weaker than gravitational force.

D. central forces.

#### SOLUTION

The nuclear force between the nucleons exists only when they are inside the nucleus and hence, it is a short range force.

Q. 91 Which of the following is False about nuclear forces?

A. It varies inversely with distance

B. It is basically an attractive force

C. It is the weakest force operating in nature

D. It is non central force

#### SOLUTION

Nuclear force is the strongest force operating in nature.

Q. 92 Match the items in list A with suitable items in list B. List A List B A Sonar (I) Electromagnetic induction B Aero plane (II) Newton’s second and third laws of motion C Rocket propulsion (III) Reflection of ultrasonic waves D Electric Generator (IV) Bernoulli’s theorem

A. A-II, B-III, C-I, D-IV

B. A-III, B-IV, C-II, D-I

C. A-IV, B-I, C-III, D-II

D. A-I, B-II, C-IV, D-III

#### SOLUTION

The technologies in list A are based on one of the principles in list B. Technology Principle A Sonar (III) Reflection of ultrasonic waves B Aero plane (IV) Bernoulli’s theorem C Rocket propulsion (II) Newton’s second and third laws of motion D Electric Generator (I) Electromagnetic induction

Q. 93 The theory of invariance in nature and the theory covering the motion of the high-speed particles is

A. theory of electromagnetism

B. theory of electromagnetic induction

C. theory of quantum mechanics

D. theory of relativity

#### SOLUTION

The theory of electromagnetism deals with the study of electric and magnetic phenomenon. The theory of electromagnetic induction deals with the production of electromotive force across a conductor when it is placed in a time varying magnetic field. The theory of quantum mechanics deals with the microscopic domain. The theory of relativity deals with the particles moving with speed of the order of the velocity of light.

Q. 94 Optics involves the study of various phenomena connected with

A. Light

B. Magnetism

C. Electricity

D. Electronics

#### SOLUTION

Optics is the branch of physics that deals with the phenomenon of light.

Q. 95 -mesons are the field particles of

A. Gravitational forces

B. Weak interactions

C. Nuclear forces

D. Electromagnetic forces

#### SOLUTION

The forces operating inside the nucleus are called nuclear or strong forces. In general, the forces that are responsible for the interaction between mesons, between baryons and between baryons and mesons are called nuclear forces. Thus, nuclear force is due to the interaction between nucleons (baryons) and - mesons. The - mesons (o, + and ) are the field particles for the nuclear forces.

Q. 96 -decay is due to

A. Gravitational forces

B. Weak interactions

C. Nuclear forces

D. Electromagnetic forces

#### SOLUTION

The process of -decay is due to weak interaction. In -decay, a neutron inside the nucleus changes into a proton by emitting an electron and an uncharged particle, called antineutrino  . The -decay may be represented as below:   During weak interaction, the two particles are in contact or exactly overlap each other.

Q. 97 Who Discovered the Law of force acting between Charges?

A. Kelvin

B. Coulomb

C. Einstein

D. Newton

#### SOLUTION

The force acting between two charges is given by Coulomb's law.

Q. 98 Which of the following laws holds good in all natural processes?

A. Newton's law of gravitation

B. Coulomb's law of electric charges

C. Faraday's law of electromagnetic induction

D. Hooke's law

#### SOLUTION

Newton's law of gravitation is applicable to every body. Coulomb's law is applicable only to electrically charged bodies. Faraday's laws of electromagnetic conduction are applicable to conducting bodies placed in changing magnetic field. Hooke's law is applicable to bodies within elastic limits.

Q. 99 Who discovered the electron?

A. Hertz

B. J.J. Thomson

C. E.O. Lawrence

D. C.V. Raman

#### SOLUTION

It was known by 1900 that the atom was not a simple, indivisible particle but contained at least one sub-atomic particle called electron which was identified by J.J. Thomson.

Q. 100 Which of the following discovery is associated with the name of S. Chandrasekhar?

A. Structure and evolution of stars

B. Scattering of light by molecules

C. laws of electromagnetic induction

D. Principle of buoyancy