A point source `S` of light is emitting a power `P`. A sphere of radius `r` is situated at a distance `R` from source `S( r lt lt R)`, has a mass `M` and specific heat capacity `C`. The time in which temperature of sphere rises by `theta^(@)C` is

If charge q is induced on outer surface of sphere of radius R, then intensity at a point P at a distance S from its centre is

A mono chromatic light source of wave length I is placed at a distance R from the mirror as shown and a spherical screen of radius R is at a distance R from the source as shown in the figure and point P is on the sphere nearest to the source.It R is two times the wave length (R=2l) then f'+(p)

A point source of constant power P is emitting photon of wavelength lambda . What is the intensity of photons at r distance from the source ?(speed of light = c)

P is a point at a distance r from the centre of a spherical shell of mass M and radius a, where r lt a . The gravitational potential at P is

P is a point at a distance r from the centre of a spherical shell of mass M and radius a, where r lt a. The gravitational potential at P is

The internal surface of the walls of a sphere is specular. The radius of the sphere is R=36cm. A point source S is placed at a distance R//2 from the cneter of the sphere and sends light to the remote part of the sphere. Where will the image of the source be after two successive reflections from the remote and then nearest wall of the sphere? How will the position of the image change if the source sends light to the nearest wall first?Consider paraxial rays.