A coil has inductive reactance $3$ H. The ratio of its reactance when it is first connected to an a.c. source and then to d.c. source is

An equiconvex lens of focal length F is cut in to two equal parts along the vertical axis. The focal length of each part will be

A ray of light travels from air to water to glass and again from glass to air. Refractive index of water with respect to air is 'x', glass with respect to water is 'y' and air with respect to glass is 'z'. Which one of the following is correct?

When the distance of separation between the slit and screen is doubled, the angular separation between fringes in single slit diffraction pattern experiment