Question

an object 4 cm in size is placed at 30 cm in front of concave mirror of focal length 20 cm. At what distance from the mirror should a screen be placed to obtain a sharp image?Find nature and size of Image​

Answer 1

Answer:

Explanation:Here, h1=4cm,u=−30cm,f=−20cm,v=?

v=?, h2=?

From mirror formula

1/v+1/u=1/f

1/v=1/f−1/u  =

v=−60cm

∴ the Distance of screen from the mirror =60cm

As h2/h1 = −v/u =-60/30=−2

h2=−2h1 =−2×4=−8cm

the Negative sign is for inverted image.

Answer 2

Solution. Negative sign indicates that the image is in front of the mirror. Therefore, the screen must be placed in front of the mirror at a distance of 37.5 cm.