# Lens refraction problems

1. Mar 1, 2009

### jakey

1. The problem statement, all variables and given/known data
The property of a transparent material that makes it useful for a lens is: this is refraction, right?

In relation to this, the image of an object can't be focused correctly if a simple glass lens is placed under white light because:
a)the lens absorbs light
b)the glass has some coloration due to impurities
c)the surface of the lens reflect some light
d)a glass prism splits sunlight into different colors
e)glass absorbs UV light

2. Relevant equations

none

3. The attempt at a solution
I'm thinking that the answer is D. This is because white light contains many wavelengths, it is not monochromatic. Because of this, when they pass through the lens, some of the wavelength may interfere. This is why it can't be focused correctly.

In relation to this, white light is split into different colors when it passes thru the prism.

is this right? thanks

2. Mar 1, 2009

### tiny-tim

Hi jakey!

D is right, and your reason "it can't be focused correctly" is also right …

but your reason why it can't is wrong …

I suggest you re-think "some of the wavelength may interfere" … isn't interference what makes lenses work?

and can two different wavelengths of light interfere?

3. Mar 1, 2009

### jakey

Re: Lens

really? i would just like to clarify first, refraction also happens in a lens right?

isn't it that when they pass through the lens, some of the wavelenghths may be out of phase and thus some would cancel, some would interfere constructively?

4. Mar 1, 2009

### tiny-tim

yes, interference between light of the same wavelength causes refraction etc

5. Mar 1, 2009

### jakey

Re: Lens

and because white light isnt monochromatic, then it cant be focused correctly. thanks!:)