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Transcript of Waves
Most waves need a medium to travel through
They're called mechanical waves Mechanical waves form when a medium vibrate
Vibration: a back-and-forth or up-and-down motion
Moving objects have energy which transfer to a medium to produce waves. Transverse waves
Surface waves A disturbance in which energy is transferred from one place to another. Transverse Waves move in One Direction
Vibrates the medium perpendicular to the direction in which it travels
Crest: highest point
Trough: lowest point Longitudinal Vibrates medium in same direction as the wave travels
Spacing between the coils varies
Compression: coils close together.
Rarefaction: spread-out coils Surface Waves Transverse and longitudinal waves combined
Travels along the surface separating two mediums e.g. ocean
Up-and-down and back-and-forth movements combine to make each particle of water move in circle. Properties of Waves Amplitude
Speed Amplitude Maximum distance the medium vibrates from the rest position.
High waves have more energy than low waves.
Greater the energy of wave, greater the amplitude.
Dense compressions= high amplitude (for longitudinal wave) Wavelength Distance between two corresponding parts of a wave
Measure from crest to crest of transverse wave
Measure distance between two compressions for longitudinal wave Frequency Number of times a wave passes a point in a certain amount of time
Hertz (Hz): number of waves per second Speed Distance a wave travels in a given amount of time
Speed of wave = distance travelled ÷ time taken Formulae Speed = wavelength x frequency
Frequency = speed ÷ wavelength
wavelength = speed ÷ frequency Changing Direction Reflection
Diffraction Reflection The bouncing back of a wave when it hits a surface through which it cannot pass The echo you hear when you shout in an empty room Reflection Examples Looking at the mirror is reflected light Refraction The bending of waves as they enter a new medium at an angle
Caused by a change in speed Diffraction The bending or spreading of waves as they move around a barrier or pass through an opening The interaction between waves that meet Interference 2 Types: Constructive Interference
Destructive interference Constructive Interference 2 waves combine to make a wave with an amplitude larger than the amplitude of the individual waves
2 crests overlap- higher crest
2 troughs overlap- deeper trough Destructive Interference 2 waves combine to make a wave with an amplitude smaller than the amplitude of the individual waves. Standing Waves Appears to stand in one place even though it is two waves interfering as they pass through each other. Nodes & Antinodes Node: A point of zero amplitude on a standing wave
Antinode: A point of maximum amplitude on a standing wave Resonance Increase in the amplitude of a vibration
External vibration match an object's natural frequency Thank you for listening :) -S -O -D -R -S -O -R -D -S -O -D -R -D -S -S -O -D -R -S -S -O -R -D -O A B C D Answer the labeled letters. Answer A: Crest
D: Amplitude What does constructive interference add up to? What does Destructive interference add up to? Answer If wavelength is 69 and frequency is 753 then what is the speed? The speed is 51957 Answer What do standing waves form? Answer It Forms : Nodes
Antinodes LET'S START THE LAB! We will show you the question; you have to raise your hand fast and answer the question. If you get it right you get a candy! The first person to raise their hand gets to answer the question. Refraction Example Riding a skateboard with one wheel on the sidewalk and the other on grass; difference in speed causes it to change direction -S By: Salamah, Daphne, Riya and Oorja What are Waves? What are Waves? 3 Types of Waves 3 Types of Waves Properties Changing Direction Interference Standing Waves Resonance Example When pushing a swing, it goes higher and higher if you push it in time with its natural frequency QUIZ!!! -S http://www.brainpop.com/science/energy/waves/