Question # 1

A human eye can detect the electromagnetic radiations of the type:

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Infrared radiations

For- infrared radiations

X-rays radiations

Red radiations

In photoelectric effect, electrons are emitted:

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Slowly

Intermittently

Both (a) & (b)

Instantly

In Compton effect, it was considered that X-rays consist of:

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Electrons

Positrons

Photons

All of these

At constant temperature, if the density of the gas is increased, its pressure will:

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Decrease

Increase

Remain unchanged

None of these

Beta particles have less ionizing power than that of alpha particles because:

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Their smaller energy

Their smaller mass

Their smaller density

Their smaller charge

Potassium cathode in photocell emits electrons for a light:

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Visible

Infrared

Ultraviolet

X-rays

A thorium nucleus is formed when a uranium nucleus emits an 𝑎 −particles. Atomic number of thorium is :

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23

60

90

70

Speedometer of an automobile measures

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Average velocity

Instantaneous velocity

Acceleration

Instantaneous speed

Avogadro number is known as number of molecules in:

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One kg of a substance

Unit volume of a substance

One mole of a substance

None of these

The half-life of a radioactive element which has only 1//32 of its original mass left after a lapse of 60 days is:

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12days

10days

22days

36days

A human eye can detect the electromagnetic radiations of the type:

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Infrared radiations

For- infrared radiations

X-rays radiations

Red radiations

Steam engine is:

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An optical system

A thermal system

A thermodynamic system

None of these

In full wave rectification by bridge the number of diodes required are

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3

4

2

5

The efficiency of half wave rectifier is:

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25.6%

1.2%

40.6%

66.6%

The junction potential for Germanium is;

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3v

0.3 v

7v

0.7 v

A 100W, 220V bulb is operated on a 110V line, the power consumed is:

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25W

75W

50W

100W

The ratio of angular speeds of minute hand and hour hand of a watch is:

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1: 12

6: 1

12: 1

1: 6

Continuous spectrum of X-rays id due to an effect known as

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Photoelectric effect

Compton effect

Heisenberg effect

Bremsstrahlung

A body is in translational equilibrium if

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P = 0

L = 0

F = 0

 = 0

The activity of a radioactive sample is 1.6 curie and half-life is 2.5 days. Its activity after 10 days will be:

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0.8 Curie

0.1Curie

0.4 Curie

0.16 Curie

If the magnitude of charge on each of two objects is doubled and the distance between them is also doubled then force between them:

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Doubled

Quadrupled

Halved

Remains same

When a radioactive nucleus emits a 𝖰 −paritcles, the mass number of the atom:

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Increases by one

Decreases by one

Remains the same

Decreases by four

An electron is moving towards high potential. Its electrical P.E:

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Increases

Remains constant

Decrease

May increase may decrease

The method by which only one half of A.C cycle is converted into direct current is called

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half wave amplification

half wave rectification

Full wave rectification

full wave amplification

Of electron of 50 keV strike a heavy target. Then radiation emitted by target will be

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Visible light

Radio waves

Ultraviolet

None of these

A ball takes ‘t’ second to fall from a height 𝒉𝟏 and ‘2t’ second to fall from a height 𝒉𝟐 then h1/h2 is:

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2

4

0.5

0.25

An engine pumps out 40 kg of water in one second. The water comes out vertically upwards with a velocity of 3ms-1 . What is the power of engine in kilowatt?

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1.2kW

120kW

12kW

1200kW

Davisson and Germer received the Nobel prize for their work on:

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Wave nature of particle

Corpuscular nature of wave

Dual nature of particle

All of them

A steady current is flowing in a conductor of non-uniform cross-section. Thecharge passing through any cross-section per unit time is

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Directly proportional to the area of cross-section

Inversely proportional to the area of cross-section

Proportional to square of the area of cross-section

Independent of the area of cross-section

When an electron in an atom goes from a lower to higher its:

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K.E. increases, P.E. decreases

K.E. increases

P.E increases

K.E. decrease, P.E. increases

The frequency of the fundamental mode of open at one organ pipe is 400 Hz. Ifone end of pipe is closed the fundamental frequency will be

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800 Hz

600 Hz

400 Hz

200 Hz

electrons from the surface of a metal when:

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It is heated to a high temperature

Radiation of suitable wavelength falls on it

Electrons of suitable velocity strike it

It is placed in a strong electric field

Choose incorrect about properties of photon

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Rest mass of photon is zero

A photon is never at rest

Photon is not deflected by electric field not by magnetic field

The velocity of photon is different in different media

The unit of work function is

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eV

Volt

Farad

Herdz

Ratio of dimension of K.E and power is:

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1:1

T:1

1:T

M:J

No entropy change is associated with:

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Isothermal

Adiabatic process

Isobaric process

None of them

Between the plates of a parallel plate condenser there is 1mm thick paper of dielectric constant 4. Itis charged at 100 volt. The electric field in volt/meter between the plates of the capacitor is:

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100

25000

100000

400000

A certain engine coverts 20% of available heat energy into work. Then its efficiency will be:

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20%

80%

50%

None of these

In uniform circular motion, the factor that remains constant is

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Linear velocity

Centripetal force

Acceleration

speed

The law of thermodynamics which discusses the condition under which heat energy is converted into and equivalent amount of work is:

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1st

2nd

3rd

None of these

One degree of thermodynamics scale of temperature is called:

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Celsius

Fahrenheit

Kelvin

Radian