Reflection And Mirrors (T3) Flashcards
What do sound and light waves do when they hit a surface?
They reflect
When sound / light waves hit a surface, the angle of incidence equals…
The angle of reflection…
Smooth surface produce strong …… when sound waves hit them and can act as ……. when light waves hit them. The waves are reflected ……. and ……. can form …….
Smooth surface produce strong echoes when sound waves hit them and can act as mirrors when light waves hit them. The waves are reflected uniformly and light can form images.
When waves hit smooth surfaces, how can they appear?
They can be focused to a point, like sunlight reflected off a concave telescope mirror.
They can appear to come from a point behind the mirror, for example a looking glass.
What happens when waves hit a rough surface?
Rough surfaces scatter sound and light in all directions.
However each tiny bit of the surface still follows the rule “the angle of incidence equals the angle of reflection”.
What is the name of a reflected sound wave?
An echo.
What is “echo sounding” and when may it be used?
Echo sounding is the use of echoes to determine distance.
Ships often use this to determine the depth of the water beneath them.
Describe how a ship uses echo sounding to determine the depth of the water beneath it…
Sound waves are emitted from the ship and travel to the seabed.
Equipment in the ship detects some of the sound waves that are reflected by the seabed.
The depth of the sea can be calculated from the time between sending the sound wave and detecting the echo.
What is the name for the system of using echoes the way they are used in echo sounding?
Sonar (SOund Navigation And Ranging)
What happens when waves hit a concave barrier?
They become curved and converge.
What happens when waves strike a convex barrier?
They are made to diverge (spread out)
Give an example of an instrument that has a concave shape and explain how this design helps it work..
Radio telescope dishes have a concave shape so that the signals they receive are made to converge onto a detector.
What is total internal reflection?
Waves going from a dense medium to a less dense medium speed up at the boundary.
Beyond a certain angle, called the critical angle, all the waves reflect back into the glass.
We say they are totally internally reflected.
When physicists draw ray diagrams that involve reflection, what is the “normal”?
A straight construction line at a right angle to the reflecting surface at the point where the light hits it.
The angle of incidence is the angle between the normal and the incident ray and the angle of reflection is the angle between the reflected ray and the normal.
If a ray strikes the surface perpendicular to the actual surface this would be an angle of incidence of 0 degrees as it would be travelling along the normal.
Briefly explain how plane mirrors work…
Plane mirrors with a perfectly flat surface give us perfect images that are said to be virtual because they are not images that could be projected onto a screen in the way that your eye focuses an image onto your retina.
The eye is tricked into thinking the reflected ray comes from behind the mirror as the object is in front of it, and it is the same size.
It is, however, back to front (laterally inverted)
