a. State the law of distances .
b. Using the law deduce that an object between F and 2F a concave mirror produces real image beyond 2F.

Explanation

a. `(1)/(v) + (1)/(u) = (1)/(f)`
u - Object distance
v - image distance
f - Focal length
b. For concave mirror, f `lt ` 0
Fro object, u `lt ` 0
For 2f `lt u lt f, ` we get `(1)/(2f) lt (1)/(u) lt (1)/(f) " " i.e., - (1)/(2f) lt - (1)/(u) lt - (1)/(f) `
`(1)/(f) - (1)/(2f) lt (1)/(f) - (1)/(u) lt (1)/(f) - (1)/(f) `
`(2- f)/(2f) lt (1)/(v) lt 0 " " [ "since" (1)/(v) = (1)/(f) - (1)/(u) ]`
i.e, `(1)/(2f) lt (1)/(v) lt 0 ` i.e., image lies on the left, beyond 2F and it is real.