Question

A candle placed 25 cm from a lens, forms an image on a screen placed 75 cm on the other end of the lens. The focal length and type of the lens should be

(a) +18.75 cm and convex lens
(b) – 18.75 cm and concave lens
(c) +20.25 cm and convex lens
(d) — 20.25 cm and concave lens ​

Answer 1

(a) +18.75 cm and convex lens

hope it helps :)

Answer 2

Answer:

+18.75cm and convex lens

Explanation:

v

1

−

u

1

=

f

1

→

75

1

−

−25

1

=

f

1

⇒

f

1

=

25

1

+

75

3

=

75

4

f=18.75cm & his the

Hence the lens should be convex.