# Homework Help: Michelson Morley Exp. Phase Difference Question

1. Oct 14, 2011

### bphili

1. The problem statement, all variables and given/known data
The problem I am misunderstanding begins with a reference to a previous problem and example. Let me begin to ask my question by showing my work for the previous problem and describe the example in reference.

(reference problem) - Ch.1, #13.

Consider a reference frame moving with uniform velocity V through the ether. Show that according to the Galilean addition law, in this reference frame a light signal traveling at an angle θ' with the direction of V has a speed of

c'=√(c2-V2sin2θ')-Vcosθ'

Verify that this gives the expected result for a parallel light signal (θ'=0 deg.) and for a perpendicular light signal (θ'=90 deg.)

(Vsinθ')2+(Vsin(π/2-θ')+c')2=c2

(Vsinθ')2+(Vcosθ'+c')2=c2

(Vcosθ'+c')2=c2-(Vsinθ')2

Vcosθ'+c'=√(c2-(Vsinθ'))

c'=√(c2-Vsinθ')-Vcosθ'

when that θ'=0 when c'=c-v', when θ'=90 c'=√(c^2-V^2)

My Problem:

Ch.1, #18)

In section 1.6 we calcualted the phase difference between the two beams of light in the Michelson-Morley interferometer on the assumption that one arm was parallel to the ether wind and the other was perpendicular. Repeat the calculation of the phase difference if one of the arms makes an angle 90 deg. with the ether wind and the other an angle 90 deg. + θ, as in fig.1.20.(Hint: use the result of problem 13, and assume V<<c.)

Thanks and I'm online because it hard to explain this without the book...

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution