DQ13B_solution - Discussion Question 13B P212, Week 13...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Discussion Question 13B P212, Week 13 Electromagnetic Waves Page 1 of 2 A laser beam travels through vacuum. The electric field of the plane electromagnetic wave produced by the laser has the form given below. The wavelength of the beam is λ = 514 nm, and the amplitude of the electric field is E 0 = 2.5 x 10 4 N/C. G E ( x , y , z , t ) = ˆ y E 0 cos( kz + ω t 45 D ) (a) In what direction is this wave propagating? What does “propagating wave” mean anyway? It means that the shape of the wave remains the same as a function of time, it just moves. The shape of the wave is determined by that cosine. As time rolls forward, how do you have to change position so that the shape looks the same ? 0 0 ˆ Lets follow a spot on the wave corresponding to cos( 45 ). This spot obeys ˆ 0 or - . Hence this spot moves along the -z axis and evidently Ey E kz t z t c kk =− ωω +ω = = = G (b) What are the magnitudes of the wave number k and angular frequency ? ( ) 8 7- 1 1 5 99 231 0 22 2 1.22 10 m ; 3.66 10 Hz 514 10 514 10 c kc k −− π× ππ π == = × ω = = = = × λ× λ × (c) Make a sketch of what the E field looks like at some moment in time.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 2

DQ13B_solution - Discussion Question 13B P212, Week 13...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online