# Waves

## Reflection

1.This is reflection off a rough surface.

2.  This is reflection off a smooth surface.

3.     i=  r                                                      Beatriz Aguilar Barreda

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## Snell's Law

We can use this to predict the path of light crossing boundaries between AIR and any TRANSPARENT medium.

Beatriz Aguilar Barreda

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## Refraction

Light waves pass through different substances at different speeds, so rays appear to bend, first one way and then the other.

Beatriz Aguilar Barreda

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## Total Internal Reflection (T.I.R.)

All of the light is reflected back inside the medium at the boundary.

Only happens when we are going from more dense to less dense. (Glass to air)

Beatriz Aguilar Barreda

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## Dispersion

V= Wavespeed

= Wavelength

F=  Frequency

Beatriz Aguilar Barreda

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## The Electromagnetic Spectrum

In order of increasing frequency and decreasing wavelength:

•          Microwaves  (Mobile phones and satellite television)
•       Infrared  (Remote controls)
•          Visible light  (Photography)
•          Ultraviolet  (Security marking)
•          X-Rays  (Medical imaging)
•         Gamma rays  (Treating cancer)

Exposure to these can be dangerous:

•        Microwaves – Heating of body tissue
•         Infrared – Skin burns
•      Ultraviolet – Skin cancer and blindness
•         X-Rays – High doses kill cells
•     Gamma rays – Genetic mutations
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## Diffraction

This BENDING of waves around obstacles is called DIFFRACTION.

Long waves DIFFRACT more than short waves.                    Beatriz Aguilar Barreda

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## Refraction

The only way you can change frequency is if we change the source.

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## Extra Stuff

angle in air > angle in material

speed in air > speed in material

wavelength in air > wavelength in material

if i<C       REFRACTION

if i=C        r=90º

if i > C      T.I.R.

Sound travels faster in more dense

Cold air is more dense than warm air.                              Beatriz Aguilar Barreda

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## Primary Colours

Red, blue and green  are called Primary Colours- they can not be made by mixing other colours, but can be used to mix other colours.

Richard Of York Gave Battle In Vain

Beatriz Aguilar Barreda

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## The Electromagnetic Spectrum

Each of these types travels at the same speed through a vacuum and different wavelenght are absorbed by different surfaces. This absorption may heat the material up or cause an alternating current.

How are E-M waves linked?

They all travel at the speed of light.

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