Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Kostyas question for angular momentum and half wave plates Half wave plate and angular momentum made me think a little bit. It took me some seconds to "swallow" the answer. :=)

Then I started to think further, whether such a plate, rotating in the right direction, could lead to a slightly shorter wavelength?

And further, what happens in an optical active substance, which "rotates" the plane of polarisation of a light beam? Of course no momentum is changed, there is only a extremely small difference of interaction of the two circular polarized waves (representing the plane polarized beam) with the substance. Is there any "mechanic" reaction of the "sample"? Might a small torque be excerted along the axis parallel to the direction of the beam?

share|improve this question
    
I believe this goes in the field of "optical tweezers". People are being very active in using light to directly act in mechanical ways on small objects (proteins, nanoparticles, etc.) –  genneth Feb 2 '11 at 21:00
1  
Could you link to the question of Kostya's that you mean? –  ptomato Feb 3 '11 at 0:15
add comment

1 Answer

up vote 2 down vote accepted

About wavelength change: In general, if you have light at frequency $f_1$ and it's modulated (in any way for any reason) at frequency $f_2$, you'll get sidebands of light at frequencies $f_1+f_2$ and $f_1-f_2$.

So yes, if you spin a half-wave plate at a constant speed, the light traveling through it will acquire sidebands at a shifted frequency and wavelength.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.