Question

Find the focal length of a double concave lens of

m= 3/ 2

and radii of

curvature 10cm, 20cm respectively.​

Answer 1

Answer:

hope it helps.........

Answer 2

Given:

A double concave lens of  m= 3/ 2  and radii of  curvature 10 cm, 20 cm respectively.

To find:

Find the focal length of a double concave lens.

Solution:

From the given information, we have the data as follows.

A double concave lens of  m = 3/ 2  and radii of  curvature 10 cm, 20 cm respectively.

⇒ μ = 3/2

⇒ R₁ = 10 cm

⇒ R₂ = 20 cm

The formula that is used to find the value of the focal length is given as follows.

1/f = (μ - 1) (1/R₁ - 1/R₂)

1/f = (3/2 - 1) (1/-10 - 1/20)

1/f = (1/2) (-3/20)

1/f = -3/40

⇒ f = - 13 cm.

Therefore, the focal length of a double concave lens is 13 cm.