You are Here: Home >< Physics

# Michelson and Morley's experiment- Special Relativity?

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. - How is there a fringe pattern? It says that the there is a path difference yet the distance to either mirror is exactly the same.

- Why does rotating it 90 degress cause a shift in the fringes?
2. bump, Anyone?
3. (Original post by SirRaza97)
- How is there a fringe pattern? It says that the there is a path difference yet the distance to either mirror is exactly the same.

- Why does rotating it 90 degress cause a shift in the fringes?
http://myslu.stlawu.edu/~jmil/physic.../michelson.gif

see diagram. The difference in path length in a typical michelson-morley interferometer is different which is why they are useful.

However... in the thought experiment if we have both arms the same length then the arm that is in the direction of motion will experience a different effective length to the other arm and rotating 90 degrees would cause a shift in the fringe pattern.

Also, there will still be a fringe pattern even if it is the same length because it is basically Young's double slit experiment. (In fact even a single beam has a fringe pattern due to diffraction!)
4. (Original post by natninja)
http://myslu.stlawu.edu/~jmil/physic.../michelson.gif

see diagram. The difference in path length in a typical michelson-morley interferometer is different which is why they are useful.

However... in the thought experiment if we have both arms the same length then the arm that is in the direction of motion will experience a different effective length to the other arm and rotating 90 degrees would cause a shift in the fringe pattern.

Also, there will still be a fringe pattern even if it is the same length because it is basically Young's double slit experiment. (In fact even a single beam has a fringe pattern due to diffraction!)
thank you

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: May 22, 2016
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:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

### Who would you like to thank?

Poll
Study resources

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

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.