# Lect23 - Physics 212 Lecture 23 Physics 212 Lecture 23...

This preview shows pages 1–10. Sign up to view the full content.

Physics 212 Lecture 23, Slide 1 Physics 212 Lecture 23

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

View Full Document
Music Who is the Artist? A) Bob Wills and the Texas Playboys B) The Viper and His Famous Orchestra C) Big Sandy and the Fly-Rite Boys D) Pokey LaFarge and the South City Three E) Blind Boy Paxton Why? They were the headliners at the CU Folk and Roots Festival this past weekend. They were wonderful !! See who you missed at: http://www.folkandroots.org/site/2011-artists
Physics 212 Lecture 23, Slide 3 Your Comments 05 “So, according to the Doppler Effect, the only thing I have to do to get X- Ray Vision is run away from whatever I want to see through? Also: would it work if said thing was running away from me? (Always looking for ways to minimize the work I have to do)” “Sometimes, you can't deny that physics is just awesome. Doppler effect seen from moving stars?? So cool!” We’ll do a Doppler shift example anyway (& discuss approximations) “This lecture was fun!” It certainly can be confusing.. We will try to make it clear !! “I don't understand what the equations mean with the (kz+-wt).” “super hard” “Can you explain the E and B electromagnetic waves graph in more detail? I'm still confused. ” “Seriously? You mispell "pointing" and then expect us to run at our iclickers so as to see the magical waves they emit? SMH”

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

View Full Document
Physics 212 Lecture 23, Slide 4 Your Comments 05 “PLEASE READ MEEEEEEEEEEEEEEE. <----- Don't post this annoying part =D I set the equations of (energy density )*(Volume) = planck's constant *(c/lambda) . Solving for lambda I see that the wavelength decreases as Volume increases. Does that mean that EM waves loose their wavelength as the Universe expands?” YES! Photons left over from the Big Bang (starting out with the energy that binds electrons to protons = hydrogen atom) have lost a lot of energy as the universe expands (from t = 400,000 years to now) λ initial 100 nm = 10 -7 m, λ today 1 mm: the cosmic microwave background
Physics 212 Lecture 23, Slide 5 Plane Waves from Last Time E and B are perpendicular and in phase Oscillate in time and space Direction of propagation given by E X B E 0 = cB 0 Argument of sin/cos gives direction of propagation

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

View Full Document
Physics 212 Lecture 23, Slide 6 Understanding the speed and direction of the wave E x z t = 0 E x = E o sin(kz- ω t) What has happened to the waveform in this time interval? It has MOVED TO THE RIGHT by λ /4 f c speed λ π ω λ ω π λ = = = = 2 2 / 4 / t = π /2 ω E x z ) cos( ) sin( 2 kz kz - = - π
Physics 212 Lecture 23, Slide 7 Checkpoint 1a “The value at t=0 is 0 for this function and it is positive in the x direction right after” “Since the sine wave is going up, its - the omega t” “The terms within the sin function show that the wave is moving in the +z direction and B is in the y plane so it's By.”

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

View Full Document
Physics 212 Lecture 23, Slide 8 No – moving in the minus z direction No – has E y rather than E x Checkpoint 1a
Physics 212 Lecture 23, Slide 9 Wavelength is equal to the speed of light divided by the frequency.

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern