Question # 1

Which of the following statement is true about soft X-rays?

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They have large wavelength

They have high energy

They have low energy

Both A and C

Intensity of light from a point source at the edge of unit sphere will be:

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𝑃

P(4π)

4𝜋

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

The minimum energy required to remove an electron is called:

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Stopping potential

Work function

Kinetic energy

None of these

Light of frequency 4f0 is incident on the metal of the threshold frequency f0. The maximum kinetic energy of the emitted photoelectrons is

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3h f0

3/2h f0

2h f0

1/2h f0

Work function of all metals varies from 2 eV to 4eV. It is 4.2 eV for Aluminum and2eV for Sodium. If these two metals are illuminated by same light, the thresholdfrequency ofAluminum is

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Less than Sodium

Equal to that of Sodium

Grater than Sodium

Can’t be decided

Figure represents a graph of kinetic energy (K) of the photoelectrons (in eV) and frequency (v) for a metal used as cathode in photoelectric experiment. The work function of metal is:

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1 eV

2 eV

1.5 eV

3 eV

According to Bohr’s theory, a line in the Ballmer series arises when the electron jumps from any of the higher orbits to the orbit with quantum number:

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1

2

3

4

What will be the number of photons emitted per second by 25 W source of monochromatic light of wavelength 600 nm:

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7.5 × 1017

7.5 × 1019

5.5 × 1019

5.5 × 1017

Which one is the correct express of de-Broglie equation for the length of atoms of mass m at temp? T(k=Boltzmann’s constant):

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An electron and a proton are accelerated through the same potential. If their masses are me and mp respectively, then the ratio of their de-Broglie wavelength is:

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1

mp/me

me/mp

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

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Photoelectric effect

Compton effect

Heisenberg effect

Bremsstrahlung

To find longest wavelength radiation in Ballmer series, the value of n used is:

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2

3

4

∞

As the intensity of incident light increases:

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Photoelectric current increases

Photoelectric current decreases

Kinetic energy of emitted photoelectrons increases

Kinetic energy of emitted photoelectrons decreases

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

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

The threshold frequency depends on the nature on:

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Natural frequency

Photosensitive anode

Photosensitive cathode

Photon

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

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

How many photons per second does a one-watt bulb emit if its efficiency is 10% and the wavelength of light is 500 nm:

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2.53 × 1017

2.53 × 1019

7.5 × 1019

7.5 × 1017

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