1. Properties of Waves
Diffraction

2. Diffraction Wide gap and narrow gap

3. Light Diffraction
Newton proposed that light may not always travel in a straight line. Christian Huygens’ designed an experiment to show, based on circular wave fronts, like dropping a drop of water in a body of water

4. Slit
When light passing through a single slit, shows a diffraction pattern that resembles interference patterns. How can a single slit create interference?

5. Light through a single slit
Secondary sources are created as the light passes through the slit and certain points. Like point A and B, the two sources will interfere with each other. There is a path difference between the two, created areas of bright interference (constructive) and dark interference (destructive).

6. Dark Fringes
We can use this to derive the angle of the first dark fringe. To have destructive interference, the path difference is half the wavelength. So the angle where the first dark fringe is located is found by:
sin 𝜃= 𝜆 𝑎
To find the next dark fringe, or the one after that etc….
sin 𝜃= 𝑛𝜆 𝑎
Where n is called the order of the dark fringe

7. Example

8. Classwork 1. 2.