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