The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $1.24 \mu \mathrm{~m}$ is incident on it. The band gap (in eV ) for the semiconductor is

In the energy band diagram of a material shown below, open circles and filled circles denote holes and electrons respectively. The material is a

The conductivity of a semiconductor increases with increase in temperature because

A) number density of free current carriers increases

B) relaxation time increases

C) both number density of carriers and relaxation time increase

D) number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density

The output of the given circuit is

A. Negatively rectified half wave

B. Positively rectified half wave

C. Negatively rectified full wave

D. Zero all times