How Wide is the Central Bright Fringe in Single Slit Diffraction?

[Mr.Sure]

Single slit diffraction

Homework Statement

Red light of wavelength 633nm from a helium-neon laser passes through a slit 0.390mm wide. The diffraction pattern is observed on a screen 3.00m away. Define the width of a bright fringe as the distance between the minima on either side.

What is the width of the central bright fringe?

What is the width of the first bright fringe on either side of the central one?

Homework Equations

asin(θ)= (m+1/2)λ

The Attempt at a Solution

I used the slit length, screen distance and wavelength to find the angle of the light.

θ = arcsin(\frac{λ}{2a})

Then I drew a triangle to find the length of the fringe.

tan(θ) = \frac{h}{3}

h = 3tan(θ)
h = .0024m

I got .0024 for h but it is wrong.

 

[Sunil Simha]

Are you familiar with the approximations to be used in a diffraction experiment?

 

[rude man]

Homework Statement

Red light of wavelength 633nm from a helium-neon laser passes through a slit 0.390mm wide. The diffraction pattern is observed on a screen 3.00m away. Define the width of a bright fringe as the distance between the minima on either side.

What is the width of the central bright fringe?

What is the width of the first bright fringe on either side of the central one?

Homework Equations

asin(θ)= (m+1/2)λ

Wrong formua. That one's for 2-slit interference, I think ...

Grab the correct formula for the angular distance between minima for a single-slit Fraunhofer diffraction experiment. Realize that the central fringe comprises two minima, one on either side of the central maximum.