- Law of reflection: Angle of incidence = angle of reflection
- θi = θr
- This is measured from the normal
Convex and concave mirror
Convex mirrors diverge the reflected light rays so that it appears behind the mirror.
- The focal point is behind the mirror
- The image is usually larger and the right way up.
Concave mirrors converge the reflected light rays so that the image appears in front of the mirror
- The focal point is in front
- The image is usually inverted and smaller
The same is true for waves – draw waves as wavefronts, which follow the same rules
- An echo is a reflection of sound
- It arrives at the listener some time after the direct sound
- A true echo is a single reflection of the sound source
- The time delay is the distance travelled divided by the speed of sound
- The human brain filters out any echoes that return within 0.1 s
- Bats, other animals and some humans have the ability to detect objects in their environment by sensing echoes from those objects.
- Echo locators actively create sounds, e.g. by tapping or screeching
- These sounds reflect off objects and are used by the person to accurately identify the objects’ location and size