An achromatic doublet is formed by combining two lenses.if the focal length of the lenses and their dispersive powers are`f,f^(')`and `omega omega^(')`respectively then

An achromatic combination of lenses is formed by joining

An achromatic combination of lenses is formed by joining

An achromatic lens-doublet is formed by placing in contact a convex lens of focal length 20 cm and a concave lens of focal length 30 cm. The dispersive power of the material of the convex lens is 0.8. Determine the dispersive power of the material of the concave lens. Calculate the focal length of the lens-doublet.

An achromatic lens-doublet is formed by placing in contact a convex lens of focal length 20 cm and a concave lens of focal length 30 cm. The dispersive power of the material of the convex lens is 0.8. Determine the dispersive power of the material of the concave lens. Calculate the focal length of the lens-doublet.

Two lenses in contact form an achromatic lens. Their focal lengths are in the ratio 2 : 3 . Their dispersive powers must be in ratio of

An achromatic doublet of focal length 90 cm is to be made of two lenses, the material one having 1.5 times the dispersive power of the other. The doublet is converging type. Find the focal length of each of lens.

Two lenses have focal lengths f_(1) and f_(2) and their dispersive powers are omega_(1) and omega_(2) respectively. They will together form an achromatic combination if