Albert Teen YOU ARE LEARNING:  Reflection at a Boundary  # Reflection at a Boundary ### Reflection at a Boundary

When waves hit a surface, they're either transmitted, absorbed or reflected. If they are reflected, they obey the law of reflection: the angle of reflection equals the angle of incidence.

In this lesson, we will look at how changing from one medium to another will affect the behaviour of a wave.

A light wave travelling through air finds a window in its path. When the light hits the glass it is... Charlie is sitting in the sun wearing a black t-shirt. He notices his t-shirt is getting very hot. This is because the light waves from the sun are getting _______ by his t-shirt. A light wave travelling through air finds a mirror in its path. When the light hits the surface it is... 1

These are the 3 types of behaviour a wave can have at the boundary of 2 media.

Some transparent media can also bend waves, but we will look at this in later lessons. 2

Let's take a closer look at reflection.

Notice that the wave is hitting the surface at an angle. This angle is measured against the normal - **** an imaginary line drawn perpendicular to the surface. What do think the "angle of incidence" might mean? The angle of incidence is defined as the angle formed by a wave incident on a surface and the normal. What do think the "angle of reflection" might mean? 1

The angle of incidence, $\theta_i$, and the angle of reflection, $\theta_r$, ​are related by the Law of Reflection. From looking at the diagram, which option do you think is a correct? A.﻿$\theta_i>\theta_r$ B.$\theta_i=\theta_r$

C.$\theta_i<\theta_r$  2

Against what are the angle of incidence and the angle of reflection measured?  What does the law of reflection state? To sum up: Waves at a boundary of mediums (for example window panes, t-shirts or mirrors) will either be transmitted, absorbed or reflected. If they are reflected, they obey the law of reflection, which states that $\theta_i=\theta_r$ .