In Newton's rings experiment, if the diameter of a certain order of a dark ring is four times that of the second ring, then what is the order of the ring?

Which of the following options could be the lowest temperature of mesosphere?

Which of the following options is the correct critical angle of a diamond?

Light falls on a spherical glass surface from a point source in air. It is given that n=1.5 for the spherical glass surface and the radius of curvature is 40 cm. At which of the following positions the image is formed. if the distance of the light source from the glass surface is 100 cm?

For a ray incident from a denser to rarer medium, what is the critical angle of incidence it?

The northern lights and the aurora occurs in which of the following layers of atmosphere?

A magnifying glass widens the angle through which _________.

Accidentally breathing foreign particles into the lungs is called _______.

A point is ____ of an inch in height.

Einstein's equivalence principle says that ______.

Fast-moving currents of air that occur above the friction layer are called _____.