Question

focal length of plano convex lens when its radius of curvature of the surface is R and n is the refractive index of the lens

Answer 1

Answer:

Figure shows a plano-convex lens of refractive index μ=n.

From Lens Maker's formula:-

f

1

=(

μ

1

μ

2

−1)(

R

1

1

−

R

2

1

)

where, μ

2

and μ

1

are refractive index of lens and surrounding medium respectively.

And, R

1

and R

2

are radius of 1st and 2nd surfaces respectively.

Here,

μ

1

=1,μ

2

=n,R

1

=−∞,R

2

=−R,f=2R

Hence,

f

1

=(n−1)(

−∞

1

−

−R

1

)

⟹

f

1

=(n−1)

R

1

⟹f=

n−1

R

hope its helpful to you.❤️