# Physics waves, light and potential dividers

Revision for waves, light and potential dividers.

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• Created by: double96
• Created on: 17-03-12 13:28

## Funky wave stuff

Constructive interface: when two waves of the same type are played at the same time (gets louder).

Destructive interface: when opposite waves cancel each other out.

When light rays pass through tray slits they SPREAD OUT this is called DIFFRACTION.

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## Dispersion if light

Visible light is made up of 7 different wavelengths. These slow down by different amounts when they hit a glass prism. Red refracts least, violet refracts most. This splits / disperses the colours.

The order of colours from top to bottom is the same as the rainbow, a way of remembering this is through the phrase; Richard Of York Gave Battle In Vain. Red, Orange, Yellow, Green, Blue, Indigo, Violet.

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## Continued from last card....

Total internal reflection.

Light is reflected internally and this is used to direct light in a camera.

Convex lenses are able to bring rays of light to a FOCUS (focal point)

Thin lenses have a long focal point and fat lenses have a short focal point.

There are 3 golden rules with dispersion of light that you must remember.

Rule 1) any ray through the opticle centre of the lens continues un deviated.

Rule 2) any ray parallel to the principle axis is refracted through the focal point.

Rule 3) any ray through the focal point is refracted parallel to the principle axis

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## Potential dividers

Thermistors: high heat = low resistance.
: low heat = high resistance.
LDR's ( light dependant resistors): bright light = low resistance

The resistance of a potential divider can be calculated by using this equation.

V out = V in times ( resistance two divided by resistance 1+ resistance two)

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