Waves: Reflection

Reflection of Waves

Reflection is the process when a wave strikes an object or surface and bounces back.
This principle applies to all types of waves, including light, sound, and water waves.
The Law of Reflection states that the angle of incidence is equal to the angle of reflection. This means, the angle at which the wave hits the surface (angle of incidence) is the same as the angle at which it bounces back (angle of reflection).
Angles in reflection are measured relative to the normal line, which is an imaginary line perpendicular to the boundary or surface at the point of incidence.

When you look into a mirror, you’re seeing light that has bounced off of you and then off the mirror, this is an example of light reflection.
Echoes are examples of sound reflection. An echo occurs when sound bounces off a distant object and returns to its source.
Reflection is always accompanied by some form of absorption or transmission, where the wave’s energy is either absorbed by the material or transmitted through it.

Reflection of waves has practical applications in many areas such as in ultrasound imaging, radar technology, and the design of musical spaces like concert halls for better sound distribution.
Periscopes use the principle of reflection with mirrors at an angle to allow the viewer to see over or around obstacles.
Radar and sonar technology are reliant on the reflection of radio or sound waves to detect objects and measure distances.
Echo sounding is a type of sonar used to determine the depth of water by transmitting sound waves into water. The time it takes for the echo to return is used to calculate the water depth.

You can demonstrate reflection of waves with a simple wave-machine made from a long slinky or using a ripple tank. Reflect the waves off a flat barrier to observe how they behave, and measure the angle of incidence and the angle of reflection.
This simple experiment can show that the Law of Reflection applies not only to light, but to all types of waves.