Lens Diameter and Focal Length?
Most recent answer: 09/23/2011
Q:
I Want to construct a simple(i.e.not costly)telescope,
so,please i want some guidence for that.
How to connect the relation between the diameter of lens and its focal lenth?
thank you!
AVINASH
- Avinash (age 32)
pune,maharastra,INDIA
- Avinash (age 32)
pune,maharastra,INDIA
A:
The diameter of a lens does not affect the focal length, f, which is give by
![\frac{1}{f} = (n-1) \left[ \frac{1}{R_1} - \frac{1}{R_2} + \frac{(n-1)d}{n R_1 R_2} \right],](http://upload.wikimedia.org/math/d/5/d/d5d9b5b95cf3fd9ea7f2549ae4ee8fa6.png)
- where n is the index of refraction of the glass, R1 and R2 are the radii of curvatures of the front and back surfaces and d is the thickness of the lens. The diameter does not enter into this equation. The diameter, D, affects the light gathering power and the resolution.
(published on 09/23/2011)