waves and the electromagnetic spectrum 8 th grade

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  • Slide 1
  • Waves and the Electromagnetic Spectrum 8 th grade
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  • What is a wave? A rhythmic disturbance that carries energy but not matter It is able to make matter move This is called a mechanical wave- it uses matter to trasfer energy
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  • Types of Mechanical waves Transverse waves- moves at a right angle to the direction of the wave Like up and down Side to side They create peaks and troughs Like a rope Radio wave
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  • Compressional waves Moves forward and backward in the direction of the wave Like an accordion Sound waves are compression waves Every sound is made by a vibration
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  • How to measure waves Amplitude- the amount of energy a wave has The distance of the crest or the trough of a wave to the midline. This is the amplitude of a wave Measure in decibels- how loud it is.
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  • Wavelength describes frequency, or how fast a wave is. Frequency= number of wavelengths per second Measured in hertz It also tells us where a wave will fall on the electromagnetic spectrum A view of all the wavelengths from very fast gamma rays To very slow radio waves The measure from one crest to another.
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  • Wavelength does not have to be equal to amplitude, they are separate Color and pitch are based on wavelength Faster wavelength= faster vibration and higher pitch Blue light has a faster frequency than red light This is what it used for photosynthesis, more energy
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  • Sound Waves travel better through dense mediums like solids. Electromagnetic waves, like light travel best in open space This is why we get light from the sun so fast But it changes direction as it hits the atmosphere
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  • Reflection and refraction reflection is when a wave bounces off an object and changes direction Echo and mirrors Refraction is when the wave slows down and changes its angle as it passes from one medium to the other. A glass with water in it
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  • refraction
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  • Doppler effect- sound waves get compressed causing a high pitch as the object gets closer to you. as the object moves past the sound waves get longer and the tone gets lower. Like a siren Blue-red shift- as light moves away from you it get red, because red has a longer wave length As light come toward you it is blue, blue has a shorter wave length
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  • Use Doppler effect to Check speed for police radar Check position of satellites Get information over stars and other planets Are they moving away or towards us, we can tell by the wavelength we receive
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  • Lenses and mirrors Concave and convex Draw and describe the differences Transparent, translucent, opaque
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  • Diffraction Bending of waves around a barrier Like a rainbow Like water waves moving around an object They separate and move around the object Remember, a wave is energy and it will keep moving untie all energy is released
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  • Wave Interference When 2 waves combine to form 1 wave Constructive interference- amplitude increases
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  • Destructive interference- amplitude decreases Occurs when trough and crest meet Used in noise canceling headphones


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