Question

A concave mirror has af local length of 20 cm. At what distance from the mirror an object be placed so that it forms an image at a distance of 30 cm from the mirror. Slaa calculate the size of the image formed.

Answer 1

Answer:

f = -20 and h of object = 4 v = -30

find u and height of image, formula is

1/v + 1/u = 1/f

1/u = 1/-20 - 1/(-30)

= 1/-20 + 1/30

= 3 - 2/60

= 1/60

as u is always negative

so u = -60

magnification = -v/u

m = -(-30) /-60

m = 30/-60

m = -1/2

m = h of image/h of object

-1/2 = h of image /4

h of image = -2