An achromatic convergent lens of focal length 20 cm is made

Last updated: 6/24/2023

An achromatic convergent lens of focal length 20 cm is made of two lenses in contact of materials having dispersive powers in the ratio of 1 2 and having focal lengths f and f respectively Which of the following is true 1 f 10 cm f 20 cm 2 f 20 cm f 10 cm 3 f 10 cm f 20 cm 4 f 20 cm fa 10 cm