A concave lens of focal length 20 cm is placed at a distance of 35 cm from an object. Find the position of the image and its magnification.

Explanation

Data supplied,
f = - 20 cm, `" " ` u = - 35 cm , v = ? , m = ?
`(1)/(f) = (1)/(v) - (1)/(u) " " (1)/(20) = (1)/(+ 35) + (1)/(v)`
`(1)/(v) = (-1)/(20) + (-1)/(35) = (-35+ 20)/(20 xx 35) = (- 55)/(700) " " v = (-700)/(55) = - 12.73 ` cm
` m = (v)/(u) = (- 12.73)/(-3.5) = 0.3637 `