1. Diffraction and Interference

2. Double Slit Diffraction
Diffraction is the bending of waves around barriers
English Physicist Thomas Young discovered that light bends around barriers as a wave.
Using the double slit experiment and monochromatic light, Young found evidence for the “wave- nature” of light

3. Double Slit Diffraction
Interference fringes are the dark and bright bands created by the double slit experiment.
Dark bands are where the light is “out of phase”, cancelling each other out
Light bands are where the light is “in phase”, adding to each other

4. Double Slit Diffraction
Demo first, then lets draw a picture of the set up to derive the wavelength of light using the double slit pattern

5. Double Slit Diffraction
Example 1: pg 395: Red light falls on two narrow slits mm apart. A first-order bright line is 21.1 mm from the central bright line on a screen m from the slits. What is the wavelength of the red light?

6. Single Slit Diffraction
If you use one slit, you can also get a diffraction pattern. You need to satisfy the following condition for it to work:
λ 𝑤 =𝑠𝑖𝑛𝜃= 𝑥 𝐿

7. Diffraction
There are two ways to break up white light into colors: diffraction and reflection.
Diffraction gratings have multiple slits that are able to break up a white light source into multiple colors.
The instrument used to measure light wavelengths with a diffraction grating is called a grating spectrometer

8. Diffraction Watch a video Do the worksheet
Homework: DUE 3/17 pg 395: 1,2 and pg 398: 5,7