Two thin lenses, one of focal length + 60 cm and the other of focal length – 20 cm are put in contact. The combined focal length is

A thin convex lens of focal length 10 cm and a thin concave lens of focal length 20 cm are in contact. The combination acts as :

A concave lens of focal length 12 cm and a convex lens of focal length 20 cm are kept in contact with each other . Find the focal length of the combination .

A thin convex lens of focal length 10 cm and a thin concave lens of focal length 26.2 cm are in contact. The combination acts as

Two thin concave lenses of focal lengths 10 cm and 30 cm and a thin convex lens of focal length 30 cm are kept in contact. What will be the power of lens combination ?

A concave lens of focal length 12 cm and a convex lens of focal length 20 cm are kept in contact with wach other. (i) Find the focal length of the combination. (ii) What will be the behaviour fo the combination ?

Two thin lenses, aone convex of focal length 10 cm and other concave lens are kept in contact to form a composite lens of focal length 13 cm . If the combination acts as a converging lense the focal length of second lens is

Two thin lenses, aone convex of focal length 10 cm and other concave lens are kept in contact to form a composite lens of focal length 13 cm . If the combination acts as a converging lense the focal length of second lens is

Two thin lenses of focal lengths 20 cm and -20 cm are placed in contact with other. The combination has a focal length equal to

Two thin lenses of focal lengths 20 cm and -20 cm are placed in contact with other. The combination has a focal length equal to

If a concave lens of focal length 12 cm and a convex lens of focal length 20 cm are kept in contact with each other . (i) Find be the focal length of the combination ? (ii) What will be the behaviour of the combination ?