# Single Slit Diffraction

## Homework Statement

A single slit illuminated by light of wavelength λ = 610 nm produces a diffraction pattern with its first minimum at 3.5 mm from the central maximum. (a) Find the slit width, and (b) For the same slit, what wavelength of light would produce a first minimum at θ = 4.0 degrees.

## Homework Equations

D = slit width
m = minima order
L = distance from the slit to the wall

D sin θ = m λ
tan θ = sin θ = θ (small angle approximation)

## The Attempt at a Solution

λ = 610 nm or 6.1 x 10^-7 m
m = 1 (first order minima)
x = 3.5 mm (which is the distance from the central maximum to the first minimum)

tan θ = x / L

D = m λ / sin θ

I would be able to solve this question if I was given either the distance from the slit to the wall (L) or the angle (θ), however, I am not given any of this, and as such, I am unsure how to proceed.

## Answers and Replies

Simon Bridge
Science Advisor
Homework Helper
It is not possible to solve the problem with the information written above.
You should complain to the person who set the problem - make sure you have read all the information given as sometimes a vital bit is someplace else. Check with other people doing the same problem - it helps to have others also complaining.

Hello David,

Please update us if the professor says it was right and then shows you how to do it. I've been thinking about this question for a bit but have not come up with a solution for you. I agree with Simon, I do not believe it can be solved as presented. But I will think about it more if I have time later this week. Please keep us updated. In the mean time don't get too caught up on it. Move on to other problems. :D

Best Regards,

Caleb P.