# P1

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## Generating Electricity

Fuel is burnt in a furnace

Water is heated to produce high pressure steam

Hot waste gases out

Steam pushes around a turbine which is like a giant fan

The turbine is attached to a generator and mkes the generator spin. The generator transforms kinetic energy to electricity energy.

Eletricity comes out

Steam is cooled in a cooling tower and condensed into water

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## Longitudinal and Transverse Waves

Longitudinal Waves:

Vibrations are parallel to the direction of energy transfer of the wave

Examples include sound waves and ultrasound, shock waves and a slinky spring when you push the end

Transverse Waves:

Vibrations are perpendicular to the direction of the energy transfer of the wave

Examples include light and other EM waves, ripples on water, waves on strings and a slinky spring wiggled up and down

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## Reflection

Reflection of light allows us to see objects. Light bounces off them into our eyes.

ANGLE OF INCIDENCE = ANGLE OF REFLECTION

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## Refraction and Diffraction

Refraction:

Through a material however go in a different direction

When a wave crosses a boundary between 2 substances (eg glass to air), it changes direction

If a light wave hits a boundary 'face on' it carries on in the same direction

If a wave meets a different medium at an angle, the wave changes direction and its been refracted

Diffraction:

The waves bend round obstacles causing the waves to spread out

Gap much wider than wavelength - little diffraction

Gap a bit wider than wavelength - diffraction only at edges

Gap the same as wavelength - maximim diffraction

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## Doppler Effect

When something that emits waves moves towards you or away from you, the wavelengths and frequencies of the waves seem different - compared to when the source of the waves is stationary

The frequency of a source moving towards you will seem higher and its wavelength willl seem shorter

The frequency of a source moving away from you will seem lower and its wavelength will seem longer

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## Red Shift

The further away a galaxy is, the greater the red shift

Measurements of the red shift suggest that all the galaxies are moving away from us very quickly

More distant galaxies are moving away from us faster than nearer ones - provides evidence that the whole universe is expanding

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