In a Frank-Hertz experiment, an electron of energy 5.6 eV passes through mercury vapour and emerges with an energy 0.7 eV. The minimum wavelength of photons emitted by mercury atoms is close to :

A load of mass M kg is suspended from a steel wire of length 2m and radius 1.0 mm in Searle's apparatus experiment. The increase in length produced in the wire is 4.0 mm. Now the load is fully immersed in a liquid of relative density 2. The relative density of the material of load is 8.

The new value of increase in length of the steel wire is:

In the figure, given that V_BB supply can vary from 0 to 5.0 V, V_CC = 5V, $$\beta $$_dc = 200, R_B = 100 k$$\Omega $$, R_C = 1 k$$\Omega $$ and V_BE = 1.0 V. The minimum base current and the input voltage at which the transistor will go to saturation, will be respectively :

When a certain photosensitive surface is illuminated with monochromatic light of frequency v, the stopping potential for the current is –V₀/2. When the surface is illuminated by monochromatic light of frequency v/2, the stopping potential is – V₀. The threshold frequency for photoelectric emission is :