do now! can you write the title “p7 waves” in your books please? (underlined with a ruler of...
TRANSCRIPT
![Page 1: Do now! Can you write the title “P7 Waves” in your books please? (Underlined with a ruler of course)](https://reader035.vdocuments.net/reader035/viewer/2022062516/56649d9c5503460f94a84e5e/html5/thumbnails/1.jpg)
Do now!
Can you write the title “P7 Waves” in your books
please? (Underlined
with a ruler of course)
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P7 Waves
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This lesson
• What is a wave?
• Longitudinal and transverse waves
• Amplitude, wavelength, frequency and period of a wave
• The relationship between frequency and period
• The wave equation
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What is a wave?
YouTube - Water bubble in Space (zero gravity)
http://www.youtube.com/watch?v=xUnadiyPTks
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Waves
Waves can transfer energy and information without a net motion of the medium through which they travel.
They involve vibrations (oscillations) of some sort.
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Waves
Waves can transfer energy and information without a net motion of the medium through which they travel.
They involve vibrations (oscillations) of some sort.
Can you do something very boring and traditional………
Can you copy this please?
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Rays
Rays highlight the direction of energy transfer.
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Transverse waves
The oscillations are perpendicular to the direction of energy transfer.
Direction of energy transfer
oscillation
peak
trough
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Transverse waves
• Water ripples
• Light
• On a rope/slinky
• Earthquake
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Longitudinal waves
The oscillations are parallel to the direction of energy transfer.
Direction of energy transfer
oscillation
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Longitudianl waves
compression
rarefraction
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Longitudinal waves
• Sound
• Slinky
• Earthquake
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Wave measurements
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Amplitude - A
The maximum displacement from the mean position.
amplitude
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Period - T
The time taken (in seconds) for one complete oscillation. It is also the time taken for a complete wave to pass a given point.
One complete wave
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Frequency - f
The number of oscillations in one second. Measured in Hertz.
50 Hz = 50 vibrations/waves/oscillations in one second.
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Period and frequency
Period and frequency are reciprocals of each other
f = 1/T T = 1/f
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Wavelength - λ
The length of one complete wave.
wavelength
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Wave speed - v
The speed at which the wave fronts pass a stationary observer.
330 m.s-1
YouTube - Bill Nye the Science Guy - 51: Waves 1/3
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The Wave Equation
v = fλv = speed (m/s)
λ = wavelength (m)
f = frequency (Hz)v
λf x
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1) A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving?
2) A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves?
3) The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound?
4) Purple light has a wavelength of around 6x10-7m and a frequency of 5x1014Hz. What is the speed of purple light?
Some example wave equation questions
0.2m
0.5m
0.6m/s
3x108m/s
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Wave equation questions
vλf x
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Let’s try some questions!
Page 125 (all the questions) and
page 136 questions 1 and 4.