GCSE Physics - Reflection

Reflection of Waves

This video covers how waves can be reflected off a boundary. It explains how to draw ray diagrams and the different types of reflection including specular and diffuse.

Three Possible Outcomes

• When a wave arrives at a boundary between two materials or mediums, three things can happen: absorption, transmission, or reflection.

• The outcome depends on the wavelength of the wave involved and the properties of the two materials.

Drawing Ray Diagrams

• To show reflection taking place, we use something called ray diagrams as well as one simple rule which is that the angle of incidence is always equal to the angle of reflection.

• To draw a ray diagram, we normally start at the bottom with the boundary between the two materials. Next, we draw our incoming ray of light and add an arrow to show that it's coming down towards the mirror. Then we draw our reflected ray by drawing a normal first which is perpendicular so exactly 90 degrees from the surface. Finally, you need to know that this point here where the incoming ray touches the boundary is called points of incidence.

Types of Reflection

• Some materials like mirrors are perfectly smooth and so all of the incoming light rays will be reflected in the same direction giving us a nice clear image like you would get if you looked in a mirror; this type is called specular reflection. Other materials though like paper have a relatively rough surface when you look at them really closely which means that even though all incoming light rays are coming down in the same direction, they will be reflected in all different directions because normals will all be pointing off in different directions due to bumps on their surfaces; this type is called diffuse or scattered reflection. In both types, however, angle of incidence is always equal to the angle of reflection.

Conclusion

• In conclusion, this video explains how waves can be reflected off a boundary and the different types of reflection including specular and diffuse. It also covers how to draw ray diagrams and the three possible outcomes when a wave arrives at a boundary between two materials or mediums.