# Light Optics Need help please

1. Jun 8, 2010

### SprintsMcgee

When a blue light from a certain filtered light source is passed through a deffraction grid with 1000 slits per cm, it produces a pattern of fringes on a screen. If the screen is placed .25 meters form the grid, find the wavelength of the blue light.

I have no idea how to even start this problem let alone solve. My teacher's philosophy is too make us do the hw for sections we havent done first then talk about and the book is of no help either. Any help would be great!!!

2. Jun 9, 2010

### cartonn30gel

Re: Light Optics!!! Need help please!!!

You need more information to be able to solve this problem. Is anything given about how where the first (or nth) fringe appears on the screen?

You can verify the fact that some information is missing by doing this: Change one of the given data and see if you can construct the same system without any flaws:

1) When red light from a certain filtered light source is passed through a diffraction grid with 1000 slits per cm, it would produce a pattern of fringes on a screen placed .25 meters away. Nothing wrong with that..

2) When blue light from a certain filtered light source is passed through a diffraction grid with 2000 slits per cm, it would produce a pattern of fringes on a screen placed .25 meters away. Nothing wrong with that either..

3) When blue light from a certain filtered light source is passed through a diffraction grid with 1000 slits per cm, it would produce a pattern of fringes on a screen placed .5 meters away. That's OK as well..

Therefore, the problem is unbound. You have one relationship between the variables in the problem; however there is more than one unknown. You can forget about this last part if it was confusing. The point is that you need to be given something else.