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QUESTION: 1

If first excitation potential of a hydrogen-like atom is *V* eV, then the ionization energy of this atom will be :

Solution:

First excitation energy

QUESTION: 2

Linear momenta of a proton and an electron are equal. Relative to an electron

Solution:

If p_{e} = p_{p},

therefore, de-Broglie wavelength of proton and electron are equal.

The correct answer is: de-Broglie wavelength of proton and electron are equal

QUESTION: 3

The wavelength of a photon and the de-Broglie wavelength of an electron and uranium atom are identical. Which one of them will have highest kinetic energy

Solution:

for photon & electron

The correct answer is: Photon

QUESTION: 4

The energy E and momentum p of photon is given by E = hv and p = h/λ, the velocity of photon will be :

Solution:

E = hc/λ put c = v

and p = h/λ

E = pv

⇒ v = E/p

The correct answer is: E/p

QUESTION: 5

In the figure six lines of emission spectrum are shown. Which of them will be absent in the absorption spectrum.

Solution:

The photon’s with energies equal to that required for upward transition A → X, A → B and A → C would be absorbed, these photons shall be absent from absorption spectrum.

The correct answer is: 1, 2, 3

QUESTION: 6

A charge particle q_{0} of mass m_{0} is projected along the y-axis at t = 0 from origin with a velocity V_{0}. If uniform electric field E_{0} also exists along the x-axis, then the time at which de-Broglie wavelength of the particle becomes half of the initial value is :

Solution:

Initial debrogle wavelength of the charge particle

After any time t,

Suppose after time t, λ becomes half of the initial value i.e.

QUESTION: 7

What voltage must be applied to an electron microscope to produce electrons of

Solution:

The correct answer is: 150 *Volt*

QUESTION: 8

In X-rays production an electron accelerated with voltage V strikes a metal target. For which of the following voltages X-rays of minimum wavelength will be produced :

Solution:

λ will be minimum for maximum accelerated voltage

The correct answer is: 40 *kV*

QUESTION: 9

In the photoelectric, if we use a monochromatic light, the *I*-*V* curve is as shown. If work function of the metal is 2*eV*, estimate the power of light used. (Assume efficiency of photo emission = 10^{–3} % *i.e.* number of photoelectrons emitted are 10^{–3} % of number of photons incident on metal.)

Solution:

The energy of incident photons is given by

(** V_{s}** is stopping potential and is work function)

Saturation current = (η is photo emission efficiency)

∴ P = 7mW

The correct answer is: 7

QUESTION: 10

In Davisson-Germer experiment the relation between the angle of diffraction θ and the grazing angle φ is.

Solution:

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