11. Dual Nature of Radiation and Matter

The dimensional formula for Plancks constant is

Two metals A and B have work functions of 2 eV and 5 V respectively. When light of wavelength 400 nm is incident,

electrons are emitted from

• A

• B

• Both A and B

• Neither A nor B

In the photoelectric effect, if the intensity of incident light increases, the

• K.E. of emitted electrons decreases

• K.E. of emitted electrons increases

• photo electric current increases

• photo electric current decreases.

The speed of the fastest photoelectron emitted from a surface of threshold wavelength 600 nm, when the surface is

irradiated by light of wavelength 400 nm is

• 9.3 x 10⁵ m s^-1

• 2 x 10⁶ m s^-1

• 2 x 10⁷ m s^-1

• 6 x 10⁵ m s^-1

The stopping voltage in photoelectric effet depends

• only on the frequency of incident photon

• only on the intensity of the incident light

• only on the nature of the surface of metal

• on the frequency of incident light and the nature of the metal

 A monochromatic source of light is placed at a distance d from a metal surface. Photoelectrons are ejected at a rate

n and with maximum KE = E. If the source is brought to a distance d/2, the rate and maximum KE of photoelectrons

become, respectively,

• 2n and E

• 2n and 2E

• 4n and E

• n and 4E

Light of frequency 1.9 times the threshold frequency is incident on photo-sensitive material. If the frequency is

halved, and intensity is doubled, the photoelectric current becomes

• double

• 0

• quadrupled

• Half

If 5% of the energy supplied to a bulb is radiated as visible light, the number of photons of visible light emitted per

second by a 100 W bulb is (assume wavelength of the visible light to be 5.6 x 10^-5 cm)

• 1.4 x 10¹⁹

• 1.4 x 10²⁰

• 2 x 10¹⁹

• 2 x 10²⁰

The critical or threshold wavelength for a photosensitive surface is 6000 Angstrom and the wavelength of the incident light is

5000 Angstrom. Then the maximum energy of the emitted electrons would be

•  0.041 eV

• 0.41 eV

• 41 eV

• 4.1 eV

The maximum kinetic energy of photo electrons varies with the frequency of the incident radiation as

• 
• 
• 
•