Light MCQs

For which of the given is luminous efficiency maximum ?

The focal length of a concave mirror is f and the distance of the object to the principal focus is p . Then the ratio of the size of the image to the size of the object is

Monochromatic light of frequency 5 x 10⁴ Hz travelling in vacuum enters a medium of refractive index 1.5. Its wavelength in the medium is :

At what distance from a screen will a 27 Cd lamp provide the same illumination as a 75 Cd lamp 15 m from the screen?

In an astronomical telescope the focal length of objective lens is 100 cm and that of eyepiece is 2 cm. The magnifying power of the telescope for the normal eye is

Large aperture objects are used in telescopes because they

Light with wavelength of 6000 A0 units has a frequency

A ray reflected successively from two plane mirrors inclined at a certain angle undergoes a deviation of 3000. Then the number of images observable is :

In order to obtain a magnification of, -0.6 (minus 0.6) with a concave mirror, the object must be placed

An object is placed 20 cm in front of a plane mirror. The mirror is moved 2 cm towards the object. The distance between the positions of the original and final images seen in the mirror is