x Turn on thread page Beta
 You are Here: Home >< Physics

# AS physics single slit diffraction watch

1. Hi,

Please could someone explain why the fringes get dimmer going outwards from the centre. All the videos I've watched explain it in terms of the diffraction grating equation which we haven't done yet.

There's also another question which I don't understand which is "describe how the appearance of fringes would change if the slits were made wider without changing their centre to centre separation.

Thanks very much for any help
2. Bump
3. (Original post by VioletPhillippo)
Hi,

Please could someone explain why the fringes get dimmer going outwards from the centre. All the videos I've watched explain it in terms of the diffraction grating equation which we haven't done yet.

There's also another question which I don't understand which is "describe how the appearance of fringes would change if the slits were made wider without changing their centre to centre separation.

Thanks very much for any help
Well you can analyse the single slit as a continuous series of tiny slits across the width of the physical slit... zero angle is favorable for getting constructive interference at the screen, you can pair off the virtual slits starting from the edges of the physical slit and see that they will have constructive interference at zero angle, so you get a large maxima here but at some other angles you can get a net small amplitude too due to a small majority of constructive interference with a significant minority of destructive.

afaik you only need to understand this qualitatively at A level.

is the second question is about Young's double slit?
4. (Original post by Joinedup)
Well you can analyse the single slit as a continuous series of tiny slits across the width of the physical slit... zero angle is favorable for getting constructive interference at the screen, you can pair off the virtual slits starting from the edges of the physical slit and see that they will have constructive interference at zero angle, so you get a large maxima here but at some other angles you can get a net small amplitude too due to a small majority of constructive interference with a significant minority of destructive.

afaik you only need to understand this qualitatively at A level.

is the second question is about Young's double slit?
Thanks very much for your help. I thought that the 2nd question was about single slit diffraction as well as it was on the page about single slit but I've noticed that in the question it says slits so now I'm not sure.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 12, 2015
Today on TSR

### University rankings 2019

Cambridge at number one

### I have imposter syndrome at Cambridge

Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE