1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Electromagnetic waves

  1. Mar 6, 2010 #1
    1. The problem statement, all variables and given/known data

    The electric components E1 and E2 of two coherent electromagnetic waves are given as follows :

    [tex]E_1=E_o\sin (\omega t-kx)[/tex]

    [tex]E_2=E_o\sin (\omega t-k(x+\delta))[/tex]

    These two waves superpose each other at a certain point . Derive the amplitude of the resultant wave in terms of k and delta .

    2. Relevant equations

    3. The attempt at a solution

    I tried adding them using the sin formulas , but i failed to express it in the form of

    [tex]A \cos \theta \sin \omega t [/tex]
  2. jcsd
  3. Mar 6, 2010 #2


    User Avatar
    Homework Helper

    The sum of the two waves can be substituted by a single one of the same angular frequency w and wavenumber k, that is

    E_o\sin (\omega t-kx)+E_o\sin (\omega t-k(x+\delta))= A\sin (\omega t-k(x+\alpha))

    You have to find the expression of A in terms of E0 and delta.

  4. Mar 6, 2010 #3
    thanks ehild , but i don really get it , i don see where is the alpha coming from ..
  5. Mar 6, 2010 #4


    User Avatar
    Homework Helper

    Alpha is a phase constant for the new wave. You can determine both alpha and the amplitude A by using the identity for the sine of the difference of angles. Have you learnt how to do it?

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook