• Reflection: Hits a wall, goes back
• Refract: Changes direction
• Interference: Sum of waves
• Diffraction: Wave spreads out

Transverse waves

A pulse is the energy origin that starts the wave. The wave speed is at which it travels at. In reflection, hard boundary is reverse direction, and soft boundary is no reverse.

Wavelength: Peak to peak. $v=f\lambda$

Longitudinal waves

Transfer of energy as a particle collides with another. Instead of peaks and troughs, there are compressions and rarefactions. However, displacement position graphs can look like transverse waves.

Two dimensional waves

Rays are normal wavefronts. Huygen’s principle: Every point on a wavefront is a source of spherical wavelets.

Snell’s law

$\frac{n_1}{n_2}=\frac{\sin {\theta }_1}{\sin {\theta }_2}=\frac{v^1}{v^2}$ hello diagram

Single slit diffraction

Formula: $\theta =\frac{\lambda }{b}$

Double slit interference

Similar amplitude and waves in phase. On the wall, there are points where the two waves are out of phase by $\pi$. Here there is destructive interference, a dark spot. They can also be exactly in phase, offset by $n\lambda$, where n is some integer. There is constructive interference here, and a bright spot. The pattern is like a double slit stuff inside a single slit diffraction pattern

For many slits, $n\lambda =d\sin \theta$