The two lenses of an achromatic doublet should have

Dispersive powers of materials used in lenses of an achromatic doublet are in the ratio 5:3 .If the focal length of concave lensis 15 cm,then the focal length of the other lens will be- (1)=-9cm (2)+9cm (3)-12cm,(4)+12cm

A : When two lenses in contact form an achromatic doublet, then the materials of the two lenses are always different. R : The dispersive powers of the materials of the two lenses are of opposite sign.

The dispersive powers of the materials of two lenses forming an achromatic combination are in the ratio of 4:3 . Effective focal length of the two lenses is + 60 cm then the focal lengths of the lenses should be

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

Name the two lenses A and B

Show that, two thin lenses kept in contact, form an achromatic doublet if they satisfy the condition. (omega)/(f)+(omega.)/(f.)=0 where the terms have their usual meaning.

To obtain an achromatic combination using the lenses of same material the two lenses should be :