Question

What is the focal length (f) of a concave mirror when 'u' is -30 and 'v' is -15

Answer 1

Answer:

mirror formula =

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

so putting the values give -

$\frac{1}{ - 15} + \frac{1}{ - 30} = \frac{1}{f} \\ = > \: \frac{ - 2 - 1}{ 30} = \frac{1}{f} \\ = > \: \frac{ - 3}{30} = \frac{1}{f}$

=> -1/10 = 1/f

=> f = -10

Hence the focal length is -10 cm