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

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

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

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

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

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

• ${}_{34}\mathrm{Se}^{ 74}, {}_{31}\mathrm{Ga}^{ 71}$

• ${}_{42}\mathrm{Mo}^{ 92}, {}_{40}\mathrm{Zr}^{ 92}$

• ${}_{38}\mathrm{Sr}^{ 84}, {}_{38}\mathrm{Sr}^{ 86}$

• ${}_{20}\mathrm{Ca}^{40}, {}_{16}\mathrm{S}^{ 32}$

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

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

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

• < 124 kV

• > 124 kV

• between 60 kV and 70 kV

• = 100 kV

120.

In photoelectric effect, the electrons are ejected from metals if the incident light has a certain minimum

• wavelength

• frequency

• amplitude

• angle of incidence