Question

How far from a lamp must a concave mirror of focal length 3m be placed in order to through an image on a screen 8 m from lamp.​

Answer 1

Answer:

we have mirror equation, (1/v) + (1/u) = 1/f ........................(1)

 

v = mirror-to-image distance = 8 m

u = mirror-to-object distance , f = focal length = 3 m

 

hence (1/8) +(1/u) = ( 1/3)  ...........................(2)

by solving eqn.(2), we get u = 4.8 m

Explanation:

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