# Interference homework problem

1. Mar 29, 2012

### physgrl

1. The problem statement, all variables and given/known data

When light is shined on thin films the interference pattern results in:

a. there is no interference pattern

*b. rainbow like colors

c. light and dark pattern with no separation of colors

d. a mirror quality reflection

e. polarization of the light

3. The attempt at a solution
I thought the answer was c because I thought all interference was seen this way but the answer key says the answer is b. Can someone explain why?
Thanks!

2. Mar 29, 2012

### NewtonianAlch

Re: Interference

http://physics.bu.edu/~duffy/py106/Diffraction.html

3. Mar 29, 2012

### physgrl

Re: Interference

but why does it happen? i understand the bright and dark fringes due to constructive and destructive interference but i dont get how we achieve the colors through that process

4. Mar 29, 2012

### Staff: Mentor

Re: Interference

The question is not well phrased because they don't specify the nature of the light being shined on the film. Does the observed pattern depend upon the wavelength of the light? What happens if the light is white light?

5. Mar 29, 2012

### physgrl

Re: Interference

it should not depend on the wavelenght right because its always going to be 1/2 a wavelength out of phase. ohhh only if its white it will be a black and white pattern so the color/colors of the light will change the pattern right?

6. Mar 29, 2012

### Staff: Mentor

Re: Interference

Are you saying that all light has the same wavelength? So every color of light will produce the same pattern in exactly the same locations?
What color is white light?

7. Mar 29, 2012

### physgrl

Re: Interference

no thats not what i meant...im saying the constructive and destructive interferences will happen in the same relative locations

all colors :)

8. Mar 29, 2012

### Staff: Mentor

Re: Interference

I do believe you've got it

9. Mar 29, 2012

### physgrl

Re: Interference

thanks! :)