Question

Why the radius of curvaturein plano.convex lens is very large?

Answer 1

hey mate here is ur ans

Firstly, 

We have the lens makers equation as 

1/f = (n-1) * ((1/R1) - (1/R2)) 

Then the focal length of a plano convex lens can be quite large. f is focal length. 

n is the refractive index 

we define in above equation R1 as the radius of curvature of one side and the R2 as the radius of curvature of other side. 

now in a plano convex lens there is a plane surface. A plane surface has radius of curvature as infinity 

now substitute and try as we notice that 1/R2 becomes 0 as R2 is infinity 

so equation becomes 

1/f = (n-1)(1/R1) 

so after plugging in the values you notice the radius of curvature in the range of 25 cm to 75 cm. 

which is quite large for a lens!