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# Waves and light

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### Waves and light

1. 1. Waves• Wave-any disturbance that transmitsenergy through matter or empty space• Medium – substance through which awave can travel (solid, liquid, gas)• Wave particles vibrate and pass theenergy to a particle next to it• Mechanical waves must use a medium totravel (sound, ocean waves)
2. 2. • Electromagnetic waves travel without amedium or in a vacuum (light waves fromthe sun)• Transverse wave-particles vibrate up anddown (wave travels forward while movingperpendicular to the forward motion) - allelectromagnetic wave• Longitudinal wave – moves back and forthparallel with the direction of the motion
3. 3. • Compression – crowded• Rarefaction-spread apart• Properties of Waves:• Amplitude-related to height, large waveheight more energy• Wavelength- distance between two crestsor compressions, shorter the wave lengththe greater the energy
4. 4. Frequency – number of waves in a given amount of time,higher the frequency the greater the energyWave speed-the speed at which a wave travels through amedium
5. 5. • Wave interactions:• Reflection – wave bounces back after hitting a barrier(sound, light, heat)• Refraction – bending of light due to a change in mediumand a change in wave speed• Diffraction-bending of waves around a barrier orthrough an opening• Interference – the combination of two or more wavesthat results in a single wave (Ex: resonance – when twoobject vibrate at the same frequency)• Absorption: energy transferred to particles of matter
6. 6. Electromagnetic waves• Consists of changing electric andmagnetic fields at right angles to eachother and can travel without a medium (ina vacuum)• Electric fields surround all electricallycharged objects by vibration which causesthe magnetic field to be created.• Energy is transferred as radiation
7. 7. • Light travels in a straight line until it strikesan object is reflected, absorbed ortransmitted• The speed of light can change dependingon the type of media (matter travelingthrough)• Light is a form of radiant energy thatmoves in transverse waves
8. 8. • EM energy from the sun are major sourceof energy on earth• Em spectrum consists of:• Radio waves, microwaves, infrared, visiblelight, ultraviolet, x-ray, and gamma rays,all move at the speed of light
9. 9. Light theory• Pythagoras (580-500) – light travels in theform of tiny particles• Einstein – EM radiation (light) was astream of particles rather than a wave ofenergy called photons and that the energyin the photon was equivalent to the masswhich meant that photons had mass.E=mc2
10. 10. • Light travels at 300,000,000 m/s through avacuum and slightly less through air andother materials• 1 light year=9,500,000,000,000 km• Closest galaxy to ours Andromeda• 21 quintrillion km or21,000,000,000,000,000,000 km or• 2.3 million light years
11. 11. • Closest star Proxima Centauri• 40,000,000,000,000 km• EM energy from the sun are major sourceof energy on earth
12. 12. Sound• Sound – energy transmitted through amedium, type: longitudinal wave• Composed of compression and rarefactionwaves• Travel in all directions way from thesource• Caused by the vibration of an object
13. 13. EM spectrum is arranged from long wavelength toshort or from low frequency to high