# An object of 5.0 cm size is placed at a distance of 20.0 cm from a converging mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed to get the sharp image?

An object of 5.0 cm size is placed at a distance of 20.0 cm from a converging mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed to get the sharp image? Also, calculate the size of the image.

by (773k points)
Object distance = u = - 20cm
Focal length = f = - 15cm

We have to find the Place at which sharp image of object is made---> basically, we have to find image distance or 'v'

.'. By formula,

-----> 1/f = 1/u + 1/v
===> 1/(-15) = 1/(-20) + 1/v
===> v = [ 20 * 15 ] / [ 15 - 20 ] = 300 / -5 = - 60cm

Hence, The screen needs to be placed at 60 cm before the Converging mirror... --> [ to enjoy your movie in HD :-) Hehe ]

Now, -v/u = image size / object size

.'. Image size = 60cm / 20cm * 5cm = 15cm

.'. The Image is going to be 15cm large....... :-) [ Really Theatrical ]