Question

27) the power of a combination of two lenses X and Y is 5D .if the focal length of lens X be 15 cm :

(a) calculate the focal length og lens Y.

(b) state the nature of lens Y.

Answer 1

a) given,X+Y = 5D 15 +Y= 5 Y = 5-15 = -10 So, focal length of lens Y = -10 cm

b) Since focal length of lens Y is negative(-10cm), the lens is concave & d image obtained will be erect & virtual.