IB Physics C.3.1 Reflection, Refraction, and Diffraction Key Definitions

The angle of incidence in the higher-index medium for which the angle of refraction is 90° (the refracted ray travels along the boundary).

Diffraction is the spreading of waves as they pass through an aperture or around an obstacle.

A ray is a line drawn perpendicular to a wavefront, indicating the direction of wave propagation.

Reflection occurs when a wave strikes a surface and bounces back into the original medium.

Refraction is the bending of a wave as it passes from one medium to another, caused by a change in the wave’s speed.

The refractive index ($n$) of a medium is a measure of how much the wave slows down in that medium compared to a vacuum.

If the angle of incidence is greater than the critical angle $\left(\theta_1>\theta_c\right)$, refraction cannot occur. Instead, all of the light reflects back into the original medium.

A wavefront is an imaginary surface that connects points on a wave that are in phase (i.e., at the same point in their oscillation cycle).