Re: Why do thicker convex lens refract more light compared to thinner ones

Actually, a thicker lens does not refract MORE light, but it does refract 
what light there is through more of an angle.  This is because the surfaces have 
more curvature than a thinner lens.  Look at a thick lens: you can see that the 
surface is more curved.

Mathematically this is described by the Lens-Maker's Equation, which is
  1/s   +   1/s'     =     (n' - n)(1/R1   -   1/R2)
  where
    s  is the distance from the object point to the lens,
    s' is the distance from the lens to the image,
    n' is the refractive index of the lens material,
    n  is the refractive index of the medium around the lens,
    R1 is the radius of curvature of the first surface of the lens, and
    R2 is the radius of curvature of the second lens surface.
 (but keep in mind that the second surface has, by convention, a negative 
radius for a typical convex lens)

By this equation you can see that a lens with more curvature, which has 
smaller surface radii, will have a larger quantity to equate the left side of 
the equation to, so the s and s' will, in general, be smaller.

The angle that a "ray" of light is bent going through a surface (and this is 
on a level that just DESCRIBES what happens without explaining WHY it happens) 
depends on the angle at which it enters and on the relative refractive indeces 
of the two substances through which the light is travelling.  This is described 
by the equation
  n sin i = n' sin r
 where n is the refractive index of the first substance (sometimes air),
       n' is the refractive index of the second stuff,
       i is the angle of incidence, and
       r is the refracted angle,
and "sin" is the sine function.

So with thicker lenses with more-curved surfaces the angles of incidence and 
the angles of refraction will be more than for a thinner lens.

I hope this helps!

John Link, MadSci Physicist