Question

If the curvature radii of a convex lens are 20 cm
each and refractive index is 1.5, the focal length of
the lens is
(A) 20 cm
(B) 40 cm
(C) 10 cm
(D) .

Answer 1

Answer:

20

Explanation:

when we apply the formula u will get it

Answer 2

Dear Student,

◆ Answer - (A)

f = 20 cm

● Explanation -

Focal length of the convex lens is calculated by -

1/f = (n-1) (1/R1 - 1/R2)

1/f = (1.5-1) (1/20 - 1/-20)

1/f = 0.5 × (1/20 + 1/20)

1/f = 0.5 × 2/20

f = 20 cm

Hence, focal length of the convex lens is 20 cm.

Thanks dear. Hope this helps you...