Question

An object is placed 40cm in front of a convex mirror .The image appears 15cm behind the mirror.what is the focal length of the mirror​

Answer 1

Answer:

1/f = 1/v+1/u

= 1/40 +(-1/15) ( according to sign convection)

= - 1/24

therefore,

f = -24

Answer 2

Here your Answer:

the mirror equation

$\frac{1}{v} + \frac{1}{u} = \frac{1}{f} \\ \\ \frac{1}{f} = \frac{u + v}{uv} = > f = \frac{uv}{u + v}$

As per the new cartesion sigh conversion, from the give data,

We get,

u = -40cm & v = 15cm

$f = \frac{( - 40)(15)}{ - 40 + 15} \: = \frac{ - 600}{ - 25} \\ = > \: 24cm.$

________________________________

Hope it helps you..!!

Mark as Brilliant.