Question

the radii of curvature of two convex lenses are 0.05m and 0.05 its refractive index is 1.5. what is its focal length​

Answer 1

Given:

R1 = + 0.05 m

R2 = - 0.05 m

μ = 1.5

To Find:

The focal length of the given convex lens.

Calculation:

- We know that the focal length can be calculated by the formula:

1/f = (μ - 1) [1/R1 - 1/R2]

⇒ 1/f = (1.5 - 1) [1/0.05 - 1/(-0.05)]

⇒ 1/f = 0.5 × [1/0.05 + 1/0.05]

⇒ 1/f = 0.5 × 2 × 1/0.05

⇒ 1/f = 1/0.05

⇒ f = 0.05 m

- So, the focal length of the given convex lens is 0.05 m.

Answer 2

Focal length f = 0.05 m

Explanation:

Given: Radius of curvature of convex lens R1 = + 0.05 m

Radius of curvature of convex lens R2 = - 0.05 m

Refractive index  μ = 1.5

Find: Focal length of the given convex lens.

Solution:

When the refractive index and radii of curvature are known, we can use the Lens maker's formula to find the focal length of the lens.

1/f = (μ - 1) [1/R1 - 1/R2]

1/f = (1.5 - 1) [1/0.05 - 1/(-0.05)]

1/f = 0.5 * [1/0.05 + 1/0.05]

1/f = 0.5 * 2/0.05

1/f = 1/0.05

Therefore focal length f = 0.05 m