Question

A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is ?​

Answer 1

Answer:

h0=10mm hi=5mm v=−30cm

Here  given ,

Now we know

m=−v u =hi ho ⇒u=−vho hi =−30×10 5 =−60 cm  Now using mirror formula  1 f =1 v +1 u =1 −30 +1 −60 =−1 20 Hence f=−20 cm

Answer 2

Answer:

-20 cm

Explanation:

 =−v u =hi ho ⇒u=−vho hi =−30×10 5 =−60 cm  Now using mirror formula  1 f =1 v +1 u =1 −30 +1 −60 =−1 20 Hence f=−20 cm