For a concave mirror

Options

A. `(f)/(2)`
B. `(3f)/(2)`
C. `(f)/(4)`
D. `(4f)/(3)`

Answer

A, B

Explanation

If image is virtual.
Then, Suppose `u=-x`, then `v=+2x`
From the mirror formula
`(1)/(u)+(1)/(v)=(1)/(f)` or`(1)/(2x)-(1)/(x)=(1)/(-f)` or `x=(f)/(2)`
If image is real, then suppose` u=-y, ` then `v=-2y`
Again applying the mirror formula,
`(1)/(-2y)-(1)/(y)=-(1)/(f)` or `(3)/(2y)=(1)/(f)rArr y=(3)/(2)f`