# Homework Help: Polarization of light

1. Jun 1, 2007

### vs5813

1. The problem statement, all variables and given/known data
QUESTION: Consider linearly polarized light of the form:

E=|E|cos(kx-wt)(ì+j)

where i and j are the standard unit vectors. What is direction of polarization of this lightwave?

2. Relevant equations

3. The attempt at a solution

this is the first time i tackle a problem like this and i'm not sure where to start..i can see the wave is traveling in the positive x-direction, and i'm guessing the i and j indicate polarization...but im not sure how
any explanations would be grrrreatly appreciated..thankyou!!!

2. Jun 1, 2007

### Staff: Mentor

I think the unit vectors are orthogonal to the x axis, and the light is propagating down the x-axis, correct?

So the sum i + j is a (non-unit) vector pointing in what direction?

3. Jun 1, 2007

### Dox

Hello.

The direction of polarization is given by the direction of the electric field. So, I guess your wave is polarized with an angle << answer deleted by berkeman >> in the (x,y)-plane measure from the x axis.

Last edited by a moderator: Jun 1, 2007
4. Jun 1, 2007

### Staff: Mentor

Hi Dox,

Please do not post solutions to homework and coursework questions. That is specifically agains the PF guidelines. We appreciate your help very much in the Homework Help forums, but please focus on tutorial help, not providing the answers. Ask questions of the original poster (OP) to help them figure out the problem on their own.

Can you think of a good question to ask the OP to prod them along? I gave some hints in my post as well.

5. Jun 1, 2007

### Dox

Oh! I'm so sorry. It won't happen again.

6. Jun 2, 2007

### vs5813

ooh

oh, i see..so in this case I could say it is travelling in the x direction, polarized to 45 degrees in the x-y plane
thankyou for the help!!

7. Jun 2, 2007

### Dox

Hello again.

Please, be care... What is travelling in the x direction? The electromgnetic wave?

Cheers.

8. Jun 2, 2007

### vs5813

hmm..i would say..the direction of motion (propagation) of the light wave is the x-direction, while its polarization is at an angle..would that be correct? :uhh:

9. Jun 2, 2007

### Dox

Not quiet... Think a little mor about it.

Try to imagine both the electric and the magnetic fields and the propagation of motion.(Hint: Pointing vector)