Question # 1

Threshold wavelength for metal having work function 𝝋 is 𝝀. What is the threshold wavelength for metal having work function 2 𝒊𝒔:

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/𝟐

2

4

𝝀/𝟒

If an electron is accelerated such that its K.E is 4 times of its rest mass energythen thetotal relativistic energy of electrons is about

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5 × 10–12 J

4 × 10–13 J

3 × 10–13 J

6 × 10–12 J

A photo cell receives light from a source at 50 cm away and produces 40mAcurrent inthe circuit. When the same source at is at distance 1 m from photo cell,current in the circuit will be

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20 mA

80mA

60 mA

10 mA

The shortest wavelength of X-rays emitted from an X-rays tube depends on the:

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Current in the tube

Voltage applied to the tube

Nature of gas in the tube

Nature of material of tube

What is the momentum of a photon of light of wavelength 500 nm in kgm/s:

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1.32 × 10−21

1.32 × 10−23

1.32 × 10−25

1.32 × 10−27

The maximum energy of the electrons released in a photo cell is independent of:

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Frequency of incident light

Intensity of incident light

Nature of cathode rays

None of these

Light of frequency 1.5 times the threshold frequency is incident on a photo sensitive material. If the frequency is halved and intensity is doubled the photo electric current becomes

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Four times

Half

Double

Zero

In photo electric cell, the photo electric current

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Decreases with increase in frequency of light

Depends on intensity and frequency of light

Does not depend upon the frequency of light and but depends upon intensity of light

Increases with increase in frequency of light

The momentum of the moving photon is:

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Zero

ℎ

𝜆

ℎ𝜆

In electron microscope, we use high speed electrons because them

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Penetration power is higher

Wavelength is smaller

Frequency is smaller

K.E is smaller

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

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