Question # 1

Absolute temperature can be calculated by

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Mean square velocity

Motion of the molecule

Both (A) and (B)

None of these

A monochromatic source of light is placed at a large distance d from a metal surface Photoelectrons are ejected at rate n,kinetic energy being E. If the source is brought nearer to distance d/2, the rate and kinetic energy per photoelectron become nearly

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2n and 2E

4n and 4e

4n and E

N and 4E

Copper and germanium are cooled to 70 K from room temperature then

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Resistance of copper increases while that of germanium decreases

Resistance of copper decreases while that of germanium increases

Resistance of both decreases

Resistance of both increases

A photocell with a constant p.d of V volt across it illuminated by a point source from a distance of 25 cm. When the source is moved to a distance of 1 m, the electrons emitted by the photocell

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Carry 1/4th their previous energy

Are 1/6th as numerous as before

Are 1/4th as numerous as before

Carry 1/4th their previous momentum

Angular momentum is

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Vector (axial)

Vector (polar)

Scalar

None of these

When a hydrogen atom is bombarded the atom is excited to the n = 4 state of hydrogen atom.The energy released when the atom falls from n = 4 state to the ground state is

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1.275 eV

12.75 eV

5 eV

8 eV

In case of p-n junction diode at high value of reverse bias the current rises sharply The value of reverse bias is known as

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Cut off voltage

Zener voltage

Inverse voltage

Critical voltage

The twinkling of stars is due to

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The fact that stars do not emit light continuously

The refractive index of the earth's atmosphere fluctuate

Intermittent absorption of star light by its own atmosphere

None of them

Who explained the origin of the Fraunhofer lines?

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Fraunhoffer

Kirchhoff

Fresnel

Snell

Two sources of sound are said to be coherent if

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They produce sounds of equal intensity

They produce sounds of equal frequency

They produce sound waves vibrating with the same phase

They produce sound waves with zero or constant phase difference all instant of time

The essential distinction between X-rays andγ-rays is that

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γ-rays have smaller wavelength than X-rays

γ-rays emanate from nucleus while X-rays emanate from outer part of the atom

γ-rays have greater ionizing power than X-rays

γ-rays are more penetrating than X-rays

The temperature at which the speed of sound becomes double as was at 27°C is

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273°C

0°C

927°C

1027°C

Two sources of sound are said to be coherent if

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They produce sounds of equal intensity

They produce sounds of equal frequency

They produce sound waves vibrating with the same phase

They produce sound waves with zero or constant phase different all instant of time

If the metal bob is a simple pendulum is replaced by a wooden bob, then its time period will

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Increas

Decreases

Remain the same

First A then B

A body of mass 2 kg is thrown up vertically with K.E. of 490 joules. If the acceleration due to gravity is 9.8 m/s², the height at which the K.E, of the body becomes half its original value is given by:

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50 m

12.5 m

25 m

10 m

The velocity of a particle at an instant is 10 m/s and after 5s the velocity of the particle is 20 m/s. The velocity 3s before in m/s is:

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8

4

6

7

What will be the ratio of the distance moved by a freely falling body from rest in 4th and 5th seconds of journey?

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4 : 5

7 : 9

16 : 25

1 : 1

The force between two charges 0.06 m apart is 5 N. If each charge is moved towards the other by 0.01 m, then the force between them will become

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7.20 N

11.25 N

22.50 N

45.00

With the increase of temperature viscosity

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Increase

Decrease

Remains same

Doubles

A lens behaves as a converging lens in air and a diverging lens in water. The refractive index of the material is

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Equal to unity

Equal to 1.33

Between unity and 1.33

Greater than 1.33

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