Question # 1

A proton, accelerated through a p.d V has a certain de Broglie wavelength. In order to have the same de Broglie wavelength, an 𝑎 −particles must be accelerated through a potential difference:

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4V

8V

V/4

V/8

Which of the following is not true?

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The Lyman series is a continuous spectrum

The Ballmer series is a line spectrum in the visible region

The Paschen series is a line spectrum in the infrared region

The spectral series formula can be derived from Rutherford’s model of the hydrogen atom 18. The photoelectric effect is the ejection of

The Balmer series is found in the spectrum of:

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Hydrogen

Nitrogen

Oxygen

All

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

When ultraviolet rays are incident in metal plate, then photoelectric effect does not occur. It occurs by the incidence of:

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x-rays

Infrared rays

Radio wave

Greenhouse effect

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

Maximum speed of electrons in X-rays tube which is producing X-rays photons of frequency f is

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For X-rays which of the following is not correct:

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Cause of ionization in air when they pass through it

Can be deflected by electric and magnetic fields

Can be used to detect flaws in metal casting

Travel with the speed of light

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

In photoelectric effect experiment, stopping potential depend upon

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Intensity of light

Frequency of light

Photoelectric current

Both A and B

Temperature of black body radiating at 270c is increased to 327oc, then emittedenergywill increase by

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2 times

12 times

16 times

4 times

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

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2

3

4

∞

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

de-Broglie wavelength associated with an electron moving at a speed of 1x106 ms-1 is

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4x10-10 ms-1

5x10-10 m

6x10-10 m

7x10-10 m

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

An electron in the n=1 orbit hydrogen atom is bound by 13.6 eV. If a hydrogen atom is in the n=3 state, how much energy is required to ionize it:

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13.6 eV

4.53 eV

3.4 eV

1.51eV

Light elements do not emit X-rays because

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Electrons in it have high binding energy

These materials are non- material

There is a small difference in their energy shells

Electrons in it require very large energy to remove from these materials

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

Ultraviolet radiation of 6.2 eV falls on an aluminium surface having work function ∅ = 𝟒. 𝟐 𝒆𝑽.

The kinetic energy of the fastest electron emitted is:

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4 eV

2 eV

2.2 eV

1.2 eV

The ratio of the longest and shortest wavelength of the Lyman series is approximately:

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4/3

9/4

9/5

16/7

The momentum of the moving photon is:

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Zero

ℎ

𝜆

ℎ𝜆

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