Polarisation of electromagnetic waves?

[smileandbehappy]

I have an a-level exam tomorrow which is really important in deciding whether I can get into uni or not. So basically I am having a panic moment. Could you PLEASE tell me how you polarize electro-magnetic waves? What is the effect of polarization? Why do we polarize waves? How can you tell if a wave is polarized? How can you unpolarize a wave?

Sorry if that's to much. Thanks in advance.

 

[Hootenanny]

http://en.wikipedia.org/wiki/Polarization

Good luck.

 

[moe_3_moe]

yes good luck

 

[smileandbehappy]

thanks very much