" two thin lenses of equal focal length but of opposite nature are pair in contact,the resultant focal length of the combination will be "

When two thin lenses are kept in contanct, the focal length of the combination is

When two thin lenses are kept in contanct, the focal length of the combination is

Two thin lenses of focal length +10 cm -5 cm are kept in contact. What is the (i) focal length and (ii) power of the combination ?

Two thin converging lenses of focal length 15 cm and 30 cm are held in contact with each other. The focal length of the combination is

Two thin converging lenses of focal length 15 cm and 30 cm are held in contact with each other. The focal length of the combination is

Two lenses of focal lengths 0.20 m and 0.30 m are kept in contact with each other. Calculate the resultant focal length of the combination. Also calculate the powers of the individual lenses and that of the equivalent lens.