The plane faces fo two identical plano-convex lenses each having a focal length of 50 cm are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is

Options

A. 50 cm
B. 25 cm
C. 100 cm
D. 40 cm

Answer

A

Explanation

The focal length of the combination is
`(1)/(F) = (1)/(f_(1))+(1)/(f_(2))`
Given, `f_(1) = 50 cm and F_(2) 50 cm`
`therefore (1)/(F) = (1)/(50) + (1)/(50) = (2)/(50)`
`rArr F = (50)/(2) = 25 cm`
Object when placed at centre of curvature forms a real, inverted image of same size as object
` = (2xx 25 = 50 cm)`