A person wants a real image of his own, 3 times enlarged. Where should he stand infront of a concave mirror of radius of curvature 30 cm?

Options

A. 20cm
B. 90cm
C. 30cm
D. 10cm

Answer

A

Explanation

For real `m= -3`
`m= - 3 = -(v)/(u) rArr v= 3u`
`(1)/(v)+ (1)/(u) = (1)/(f) rArr (1)/(3u) + (1)/(u) = (1)/(-15) rArr (4)/(3u)= -(1)/(15) rArr u= - 20m`