Question

if a concave lens has focal length of 15 cm . At what distance should be the object from the lens be placed so that form an image at 10 cm from the lens​

Answer 1

Answer:

u = -30

Explanation:

f = -15 (concave lens)

u = ?

v = -10 (concave lens)

1/v - 1/u = 1/f

(1/-10) - (1/u) = (1/-15)

-(1/u) = -(1/15)+(1/10)

-(1/u) = (-2+3)/30

-(1/u) = 1/30

-u = 30

u= -30