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Dual Nature of Radiation and Matter

Multiple Choice Questions

181.

Which of the following figures represents the variation of the particle momentum and associated de-Broglie wavelength?

182.

A and B are two metals with threshold frequencies 1.8 x 10¹⁴ Hz and 2.2 10¹⁴ Hz. Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted by (Take h = 6.6 x 10^-34 J-s)

B alone
A alone
Neither A nor B
Both A and B

183.

The emission electron is possible by

photoelectric effect
thermionic effect
both (a) and (b)
none of the above

184.

An electron and a proton are possessing the same amount of kinetic energies. The de-Broglie wavelength is greater for :

electron
proton
both same
none of these

185.

If the work function of a metal is 4.2 eV, the cut-off wavelength is :

8000 Å
7000 Å
1472 Å
2950 Å

186.
The wavelength of light coming from a distant galaxy is found to be 0.5% greater than the wavelength of light coming from a stationary source. The galaxy is

coming towards earth with velocity of light

moving away from earth with velocity 1.5 x 10⁶ m/sec

stationary with respect to earth

moving away from earth with velocity of light

moving away from earth with velocity 1.5 x 10⁶ m/sec

Wavelength displacement

$∆ λ = \frac{v}{c} λ$ ------------- (1)

Suppose the wavelength coming from a source on the earth = $λ$

and the wavelength coming from galaxy = $λ^{'}$

$λ^{'}$ = (1+0.5%) $λ$

= 1.005 $λ$

or $\frac{λ^{'}}{λ}$ = 1.005

or $\frac{∆ λ}{λ}$ = $\frac{λ^{'} - λ}{λ}$

or $\frac{∆ λ}{λ}$ = $(\frac{λ^{'}}{λ} - 1)$

or $\frac{∆ λ}{λ}$ = 1.005 - 1

or $\frac{∆ λ}{λ}$ = 0.005

$∴$ $\frac{∆ λ}{λ}$ = $\frac{v}{c}$

$\Rightarrow$ 0.005 = $\frac{v}{3 \times 10^{8}}$

$\Rightarrow$ v = 0.005 × 3 × 10⁸

= 1.5 × 10⁶ m/s

Since,wavelength is increasing,therefore galaxy is moving away from the earth with a velocity of 1.5 × 10⁶ m/s.

187.

Wave nature of light does not explain

Interference
Total internal reflection
Photo-electric effect
Refraction

188.

The light of frequency v falls on a certain photoelectric substance of threshold frequency v₀. The work function of the substance is

hv₀
hv
$\frac{hγ}{v_{0}}$
h(v - v₀)

189.

The energy of a photon corresponding to the visible light of maximum wavelength is approximately

1 eV
1.6 eV
3.2 eV
7 eV

190.

The rest mass of the photon is

zero
infinite
between zero and infinite
equal to that of electron