Question

A 2 cm high object is placed at a distance of 30 cm from a concave mirror. The image is real, inverted and 3 cm in size. Find the focal length of the mirror and the position where the image is formed?

Answer 1

Explanation:

ho=2cm

u=-30cm

hi=3cm

f=?

v=?

m=hi -v

---- = -----

ho u

m= 3 -v

----- = ----

2. -30

m= -2v = -90

v= -90

-------

2

v = -45cm

f= 1/v +1/u

= 1/-45 + 1/-30

= 8+12/360

= 20/360

= 18cm