1. what is the mass of a photon? 2. does a photon have momentum? 3. using your compton notesheet,...
TRANSCRIPT
1. What is the mass of a photon?
2. Does a photon have momentum?
3. Using your Compton notesheet, find an equation that uses momentum.
Do Now (3/13/14) (5 minutes)
De Broglie WavelengthMr. Davis Baltimore Poly
Physics 1 Momentum
What equation did you learn last year for momentum?
P=mv
Momentum = Mass*Velocity
Einstein
What is Einstein’s Famous
Equation?
E= mc2
Momentum of Particles
For a particle with zero momentum p = 0:
A light photon has m = 0, but it does have momentum p:
E = mc2
E = pc
What is one way Light, or Photons, act as a wave?
Interference Reflection Dispersion
Photons
What is one way Light, or Photons, act as a particle?
Compton Effect Photoelectric Effect
Photons
De Broglie
Louis de Broglie hypothesized that because photons have wave properties, all matter could have wave properties.
He was the first person to win a Nobel Prize in Physics for something that he did in his doctoral dissertation.
Waves and Particles
What is a property that all waves have?
Wavelength!!!
If Matter acts like a wave, it should have a _________?
Waves and Particles
Lets find the wavelength of a photon.
Using the equations from the Do Now, Solve for the wavelength in terms of
momentum
h
p
De Broglie Wavelength of a photon:
hcpcE
de Broglie Wavelength:
All objects have wavelengths which can be found from their momentum
Substitute in what we know about momentum of objects with mass to the
previous de Broglie equation!
de Broglie Wavelength:
h
mv
Practice (2 Minutes)
Calculate the de Broglie wavelength for an electron moving at 10 7 m/s.
Mass of an electron: 9.1x10-
31kg
7.28x10-11m
Tuesday
•That’s all there is to de Broglie.
•Tuesday we will have a 20 minute “mini-quiz”
•It’s short!! It will be on a half sheet of paper
You have the rest of class to work on your classwork.
You will have an exit ticket at the end of class.
Use SI units (kg, m, ect)
Classwork
If Mr. Davis runs at 4.38 m/s and is 60kg. What is his de Broglie wavelength?
Bonus: ◦ How many minutes does it take him to finish a
half marathon, 21km.◦ How fast per mile does Mr. Davis run if a mile is
1600m. (For example 8:10 minutes per mile)
Exit Ticket (3/13/14) (7 minutes)
Do Now (3/18/14) (4 minutes) Calculate the de Broglie wavelength for a 50 g ball thrown with a speed of 25 m/s.
The de Broglie wavelength of an object depends on what two variables?
Mass Velocity
de Broglie Wavelength
Which of the following has the longest de Broglie wavelength if they were
moving at the same speed?
◦ A marble◦ A Baseball◦ A Car◦ The Earth
Longer Wavelength (2 Minutes)
Calculate the de Broglie wavelength of a .5kg basketball sitting stationary on the ground.
de Broglie Wavelength (2 minutes)
It’s undefined, because the object is stationary.
You have the rest of class to work on your classwork “de Broglie Wavelength”.
There is a bonus classwork if you finish early.
You will have an exit ticket at the end of class.
Classwork
Design and solve your own de Broglie wavelength problem!
Your problem should be at least two sentences and make your problem involve stuff you can touch and see.
Bonus points for creative problems!!!
Exit Ticket (3/17/14)
de Broglie Quiz Review