When the motor of an electric refrigerator starts, the lights in the house become dim momentarily. Why?

When the light is bright, the pupil becomes…. .

When an electric current is passed through a metallic conductor, heat is produced. Why?

Can X -rays show photo electric effect with visible light, if yes why?

Why does a motor take more current when we start it?

The photoelectric emission from a surface starts only when the light incident upon the surface has certain minimum:

The angle of elevation theta of the top of a light house, as seen by a person on the ground, is such that tan theta=5/2 , When the person moves a distance of 240 m. towards the light house, the angle of elevation becomes phi such that tan theta=3/4 . Find the height of the light house.

When a strip of copper is placed in the solution of silver nitrate, the solution become blue. Why ?