41.

The symbolic representation of four logic gates


The logic symbols for OR, NOT and NAND gates are respectively

• (iii), (iv), (ii)

• (iv), (i), (iii)

• (iv), (ii), (i)

• (iv), (ii), (i)

A transistor is operated in common-emitter configuration at V_c = 2 volts such that a  change in the base current from 100 μ A to 200 μ A produces a change in the collector current from 5 mA to 10 mA. The current gain is

• 75

• 100

• 150

• 150

In a Rutherford scattering experiment when a projectile of charge Z₁ and mass M₁ approaches a target nucleus of charge Z₂ and mass M₂, the distance of closest approach is r_o.The energy of the projectile is 

• directly proportional to M₁ x M₂

• directly proportional to Z₁Z₂

• inversely proportional to Z₁

• inversely proportional to Z₁

The ionisation energy of the electron in the hydrogen atom in its ground state is 13.6 eV. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between

• n = 3 to n =2 states

• n = 3 to n = 1 states

• n = 2 to n = 1 states

• n = 2 to n = 1 states

The mean free path of electrons in a metal is 4 x 10^-8 m. The electric field which can give on an average 2 eV energy to an electron in the metal will be in unit of V m^-1

• 8 x 10⁷

• 5 x 10^-11

• 8 x 10^-11

• 8 x 10^-11

The number  of photoelectrons emitted from light of a frequency v (higher than the threshold frequency v_o) is proportional to 

• v-v_o

• threshold frequency (v_o)

• the intensity of light

• the intensity of light

Monochromatic light of wavelength 667 nm is produced by a helium-neon laser. The power emitted is 9 mW. The number of photons arriving per second on the average at a target irradiated by this beam is 

• 9 x 10¹⁷

• 3 x 10¹⁶

• 9 x 10¹⁵

• 9 x 10¹⁵

The figure shows a plot of photocurrent versus anode potential for a photosensitive surface for three different radiations. Which one of the following is a correct statement?

• Curves a and b represent incident radiations of different frequencies and different intesities

• Curves a and b represent incident radiations of same frequency but of different intesities

• Curves b and c represent incident radiations of different frequencies and different intensities

• Curves b and c represent incident radiations of different frequencies and different intensities