# AS Physics - Unit 2

Revision cards for Unit 2.

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## Nature of Waves

Waves transfer energy away from its source

Progressive (moving) waves carrier energy from one place to another without transferring any material.

•  Electromagnetic waves cause things to heat up
• X-rays and gama rays knock electrons out of their orbits, causing ionisation
• Loud sound make things vibrate
• Wave power can be used to generate electricity
• Since waves carry energy away, the source of the wave loses energy
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## Waves

• Displacement, X, (in meters) - how far a point on a wave has moved from its undisturbed position
• Amplitude, a, (in meters) - maximum displacement
• Wavelength, λ, (in meters) - the length of one whole wave, from crest to crest or trough to trough.
• Period, T, (in seconds) - time taken for a whole vibration
• Frquenc, f, (in Hertz) - number of vibrations per second passing over a given point
• Phase difference (measured in degrees or radians) - amount of which one wave lags behind another.

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## Reflection and Refraction and Frequency

Reflection and Refraction

• Reflection - wave bounces back when it hits the boundary.
• Refraction - wave changes direction as it enters a different medium.

Frequency - inverse of the time period

Frequency = 1 / period

Units 1Hz = 1s-1

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## Comments

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