Question # 1

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

A proton and an 𝑎 − 𝒑𝒂𝒓𝒕𝒊𝒄𝒍𝒆 are accelerated through same voltage, the ratio of their de- Broglie wavelength will be:

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1:2

√2: 1

2√2: 1

2:1

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

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

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

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

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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

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 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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The hydrogen atoms are excited to the stationary state designated by the principal quantum number n=4, the number of maximum spectral lines are observe:

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2

3

4

6

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

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Photoelectric effect

Compton effect

Heisenberg effect

Bremsstrahlung

The potential difference applied to an X-rays tube is increased. As a result, in the emitted radiation

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The intensity increases

The minimum wavelength decrease

The intensity remains unchanged

Both B & C

In photoelectric effect experiment, stopping potential depend upon

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Intensity of light

Frequency of light

Photoelectric current

Both A and B

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

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

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2

3

4

∞

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

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

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

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𝑃

P(4π)

4𝜋

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

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