An object 4 cm in height, is placed at 15cm in front of a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed to obtain a sharp image of the object? Calculate the height of the image?

Explanation

Here, `h_(1)=4 cm,u= -15 cm,f = -10 cm,v=?`
`v = ?`, `h_(2) = ?`
From mirror formula
`(1)/(v) +1/u =(1)/(f)`
`(1)/(v) = (1)/(f)-1/u=1/-10+1/15= (-1)/(30)`
`v = - 30cm`
`:.` Distance of screen from the mirror `= 30cm`
As `(h_(2))/(h_(1))= (-v)/(u) = (+30)/(-15)= -2`
`h_(2) = -2 h_(1)= -2xx4= -8 cm`
Negative sign is for inverted image.