Register to reply

Thickness of lens and its focal length

by wlkks
Tags: focal, length, lens, thickness
Share this thread:
Mar10-10, 02:12 AM
P: 1
I'd like to ask
does thinner convex lens give a shorter focal length?

If so, why is it?

thanks very much~~
Phys.Org News Partner Physics news on
Step lightly: All-optical transistor triggered by single photon promises advances in quantum applications
The unifying framework of symmetry reveals properties of a broad range of physical systems
What time is it in the universe?
Mar11-10, 10:20 AM
P: 6
Hi there,

The focal length of lens depends on curvature of the lens and the difference between the curved surfaces, as given by the lensmaker equation.

[tex]\frac{1}{f} = (n-1)[\frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{(n-1)d}{nR_{1}R_{2}}] [/tex]


f is the focal length of the lens,
n is the refractive index of the lens material,
R1 is the radius of curvature of the lens surface closest to the light source,
R2 is the radius of curvature of the lens surface farthest from the light source, and
d is the thickness of the lens between the curved surfaces

If you reduce d then the focal length increases. If you mean making the lens less curved and hence thinner, then the curvature of the interfaces (R1 and R2) will increase and hence the focal length will increase.

Register to reply

Related Discussions
Lens and Focal Length Introductory Physics Homework 9
Focal length of Lens Introductory Physics Homework 2
Focal length of concave lens using convex lens Introductory Physics Homework 3
Lens enquiry- focal length General Physics 3
Need help with focal length lens lab Introductory Physics Homework 1