# A 3 cm tall object is placed 18 cm in front of a concave mirror of focal length 12 cm. At what distance from the mirror should a screen be placed to s

68 views
in Physics
closed
A 3 cm tall object is placed 18 cm in front of a concave mirror of focal length 12 cm. At what distance from the mirror should a screen be placed to see a sharp image of the object on the screen. Also calculate the height of the image formed.

by (71.8k points)
selected by

Here, h_(1)=3 cm,u= - 18 cm,f = -12 cm,v=?
From (1)/(v)+1/u=(1)/(f),1/u=(1)/(f)-1/u=1/-12+1/18=(-1)/(36)
:. v = - 36cm
m=(h_(2))/(h_(1))=|v|/|u|=36/18=2,m= - 2, as image is inverted.
h_(2) = -2 h_(1)= -2xx3= -6 cm
Negative sign is for inverted image.