Can you shed some light in this for me?

[Cube777]

First off, pun was intended in the title, and second , to my understanding when lights enters one medium from another one it bends, and different wavelengths bend more and less (with 405nm with the most and 650nm the least). I know white light is composed out of 3 different colors (RGB), all three different wavelengths. Sow how is it possible that you can focus sunlight (white light) to a small spot with a magnifying glass without breaking up all the colors? The different colors should focus differently, shouldn't it? Can you please shed some light on this for me?

 

[Zeebit]

What you said is correct. The bending of light as it passes one medium to another is called refraction. Different materials have a property called the index of refraction which determines how the light bends in the material.

As far as I understand, focusing sunlight, using a magnifying glass will still result in white light because although it will bend upon entry into the glass it will still have to exit into air again, bending the light back as if negating the first bending.

I don't think this is 100% correct as I am only recalling the lessons from high school.

 

[Teslanium]

White light such as that from the Sun is composed of ALL visible wavelengths, plus some UV and IR. Not just RGB.

If you use a simple lens, that is, a lens that is a single homogeneous piece of glass, it will focus the shorter ("bluer") wavelengths a bit closer to the lens, and the longer ("redder") ones farther away; this is known as chromatic aberration. Looking at/thinking of the outer edge of a lens as a "circular prism" will clarify this.

The difference in the focal length from red to blue isn't very much at "normal" scales, this is why it's hard to see when looking at the spot of a lens focusing >BRIGHT< sunlight (blink, blink!).

To avoid this, some lenses are constructed from two or more materials with differing refractive index in an achromatic configuration which compensates for this, and the lens focuses all colors to the same point (for practical purposes); an example of this type of lens would be the triplet, commonly found in small higher quality pocket magnifiers.

Try here for lots more info:
Chromatic aberration - Wikipedia, the free encyclopedia

Hope this helps,
T.

 

[Zeebit]

Yeah nice job of COPYING my post. Congrats buddy! :beer:

 

[DrSid]

The colors will bend differently, but with single lens the difference is usually too small to notice, especially with sunlight .. the spot will be too bright. Anyway the color aberration is quite visible in most binoculars.

 

[Cube777]

Thank you for all the replies!!! :thanks:

 

[Zeebit]

Nothing personal but please someone ban this dickhead.

 

[Cube777]

Reported him