Light Flashcards
What is the law of reflection?
Angle of incidence = Angle of reflection.
What is reflection?
The change in direction of a wave front at an interface between two different media so that the wave front returns into the medium from which it originated ( it bounces back ).
What is refraction?
The change in direction of a wave as it travels from one medium into another.
- The speed of the wave changes as it enters a new medium.
- The direction doesn’t change if its travelling along the normal.
When can TIR only occur?
When light is travelling from a dense material like glass meets a less dense material like air and when the angle of incidence is greater than the critical angle.
- light speeds up and changes direction away from the normal as it goes from glass to air.
- TIR can also take place with sound.
What is the angle of incidence?
The critical angle.
- Above the critical angle, light is totally internally reflected.
What is TIR?
When light reflects entirely back into a denser medium when it travels from a denser medium into a less dense one at an angle greater than the critical.
What is specular reflection?
Waves are reflected from a smooth surface.
What is diffuse reflection?
Waves are reflected at many different angles and it occurs on a rough surface.
What is the order and colours of the visible light spectrum?
ROYGBIV
Red, Orange, Yellow, Green ,Blue , Indigo , Violet.
Longest wavelength at the red end and shortest at the violet end.
How is a colour shown?
A material appears green because it reflects green and absorbs all the other colours.
How does a filter work?
A green filter will let through ( transmit ) green light and absorb all the others.
How can you investigate refraction?
Aim:
Investigate the nature of how light waves change direction when they move from air into glass.
Apparatus:
Ray box + slits, 12 V power supply, glass block, protractor, A3 paper and a sharp pencil.
Method:
1. Put block on paper and draw around it.
2. Draw the normal line, which will be at right angles to the side of the block towards where the light will be shone.
3. Use protractor and pencil to mark on the angles of incidence form 0 to 80 in 10 intervals.
4. Starting from 0 direct the light ray towards the block and mark exit point.
5. Remove block and join the dot to the point of incidence. Measure and record the angle ( angle of refraction )
6. Repeat for the other angles.
