The dispersive powers of crown glass and flight glass are in ratio 1:2. Calcualte focal length the components of an achromatic doublet focal length 20 cm.

Find the power of a concave lens of focal length 2 meters?

The dispersive powers of the materials of the two lenses are in the ratio 4:3 .If the combination of these two lenses is of focal length 60 cm,then the focal lengths of the component lenses are:

The power of a lens is 2 dioptre its focal length will be…. .

Power of a lens is -5d, its focal length is:

Write expression for the focal length and power of a lens combination.

The dispersive pwoers of crown and flint glasses are 0.03 and 0.05 respectively.If difference in the refrative indices for blue and red colour is 0.015 for crown glass and 0.022 for flint glass,calculate the angles of the two prisms for a deviation of 2^@ without dispersion.

Two thin lenses of focal length f_1 and f_2 are placed in contant .The focal length of the composite lens will be

Two lenses f powers-1.5 and +2.75 D are kept in contact.Find the focal length of the combination.