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Dual Nature of Radiation and Matter

Multiple Choice Questions

111.

The work function of sodium is 2.3 eV. The threshold wavelength of sodium will be

2900 A^o
2500 A^o
5380 A^o
1200 A^o

112.

The minimum wavelength of X-ray emitted by X-ray tube is 0.4125 A^o. The accelerating voltage is

30 kV
50 kV
80 kV
60 kV

113.

The light rays having photons of energy 1.8 eV are falling on a metal surface having a work function 1.2 eV. What is the stopping potential to be applied to stop the emitting electrons?

3 eV
1.2 eV
0.6 eV
1.4 eV

114.

A light passing through air has wavelength 6000 A^o^. The wavelength when same ray passes through a glass slab of refractive index 1.5 will be:

2000 A^o
4000 A^o
8000 A^o
1200 A^o

115.

The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein's equation, the metals which will emit photoelectrons for a radiation length 4100 A^o is /are

none
A only
A and B only
all the three metals

116.

The nuclei of which one of the following pairs
of nuclei are isotones ?

${}_{34}{Se}^{74}, {}_{31}{Ga}^{71}$
${}_{42}{Mo}^{92}, {}_{40}{Zr}^{92}$
${}_{38}{Sr}^{84}, {}_{38}{Sr}^{86}$
${}_{20}{Ca}^{40}, {}_{16}S^{32}$

117.
The ratio of the dimensions of Planck's constant and that of the moment of inertia is the dimension of

frequency

velocity

angular momentum

time

frequency

h - Planck's constant

E - Energy of photon

$E = hν \Rightarrow [h] = \frac{[E]}{[ν]} = \frac{[M L^{2} T^{- 2}]}{[T^{- 1}]} = [M L^{2} T^{- 1}]$

And I = moment of inertia = MR²

$\Rightarrow [I] = [M] [L^{2}] = [{ML}^{2}] Hence, \frac{[h]}{[I]} = \frac{[M L^{2} T^{- 1}]}{[T^{- 1}]} = [T^{- 1}] = \frac{1}{[T]} \Rightarrow dimension of frequency$

Alternative method:-

$\frac{h}{I} = \frac{\frac{E}{ν}}{I} = \frac{E \times T}{I} = \frac{(kg m^{2} / s^{2}) \times s}{(kg m^{2})} = \frac{1}{s} = \frac{1}{time} = freauency$

Thus dimension of h/I is same as frequency.

118.

A photosensitive metallic surface has work function, h v_o, If photons of energy 2hv_o_, fall on this surface, the electrons come out with a maximum velocity of 4 x 10⁶ m/s. When the photon energy is increased to 5 hv,, then maximum velocity of photoelectrons will be

2 × 10⁶ m/s
2 × 10⁷ m/s
8 × 10⁵ m/s
8 × 10⁶ m/s

119.

Hard X-rays for the study of fractures in bones should have a minimum wavelength of 10' m. The accelerating voltage for electrons in X-ray machine should be