1. Do Now: White Boards What class and type of wave is light?
Does light require a medium? What does this mean?
At what speed does light travel?
Can light go faster or slower than this? Explain.

2. Electromagnetic Waves
Electromagnetic Waves (EM Waves) are TRANSVERSE WAVES
EM Waves DO NOT require a medium
EM WAVES are radiated by ALL objects at the SPEED OF LIGHT
Speed of Light in vacuum =
c = 3x108m/s

3. Electromagnetic Waves
Calculate the wavelength of a radio wave traveling through outer space with a frequency of 5 x 104 Hz?
Does this wavelength make sense on our table?

4. Aim: How do waves interact with different boundaries?
HW: WS

5. Two types of wave sources
Point Source
Plane Source
One point that oscillates
Like a child bobbing in the pool.
Produce circular waves
An extended (rectangular) source that oscillates.
Produce plane waves

6. Diffraction Diffraction is the bending of a wave around a barrier
Know any examples?
Consider a door cracked open, what shape does the light make?
If it didn’t bend, it would be a straight column
As you can see the light ‘fans out’ after it passes through the barrier

7. Ripple tank “A way to show wave behaviors”
Point source
Plane wave
Angled Reflection
Diffraction around a corner
Single slit
Double slit
Doppler effect
Try creating each of the different wave behaviors in your tank.

8. Point Source
Plane wave
Angled Reflection
Diffraction around a corner

9. Constructive interference
Single Slit
Double slit
Constructive interference
Doppler effect
Your own:
Towards:
High frequency
shorter wavelength
Away:
Lower frequency
longer wavelength
Motion of source

10. Huygen’s Principle A wave front is made up of WAVELETS
Each WAVELET is a POINT SOURCE of circular waves
WAVE RAYS are lines PERPENDICULAR to wave fronts that show wave travel DIRECTION

11. Huygen’s Principle Barrier blocks part of a WAVE FRONT
Remaining WAVELETS make a shorter WAVE
WAVE RAYS are BENT around CORNERS

12. Single Slit Diffraction
A small opening, or a SLIT, is also an obstacle
The amount of diffraction depends on the slit width
WIDE Slit  LESS Diffraction
NARROW Slit  MORE Diffraction

13. SINGLE SLIT DIFFRACTION
When light is diffracted, the bent light waves interfere with each other CONSTRUCTIVELY and DESTRUCTIVELY
This results in a PATTERN OF LIGHT AND DARK BANDS
Actual
Pattern
Graph of Pattern

14. More point sources diffracting at once
We are primarly concerned with option c for the regents, but this is how waves behave!

15. When Waves Meet A Boundary…
Reflect
Bend Around
Refract

16. SUMMARY How does light behave when it meets an obstacle?
How does slit width correlate to the amount of diffraction?
If diffracted light were shown on a screen, what would you see?
How is it accomplished?