Two similar thin equi-convex lenses, of focal length f each, are kept coaxially in contact with each other such that the focal length of the combination is . When the space between the two lenses is filled with glycerine (which has the same refractive index () as that of glass) then the equivalent focal length is . The ratio will be :
The refractive index of the material of a prism is and the angle of the prism is . One of the two refracting surface of the prism is made a mirror inwards, by silver coating. A beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface) if its angle of incidence on the prism is?
A beam of light from a source is incident normally on a plane mirror fixed at a certain distance from the source. The beam is reflected back as a spot on a scale placed just above the source . When the mirror is rotated through a small angle , the spot of the light is found to move through a distance on the scale. The angle is given by: