Dr Pusey www.puseyscience.com
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Recall the major characteristics of a wave
Frequency
Amplitude
Wavelength
Speed
Read and draw wave graphs
Demonstrate an understanding of the relationships between frequency, period, wavelength and wave speed.
Perform calculations using the equations:
𝑣 = 𝑓𝜆
𝑓 =1
𝑇
Horizontal interval = 5ms Vertical interval = 2 V
What are the amplitude and period of this wave?
Horizontal interval = 5ms Vertical interval = 2 V
What are the amplitude and period of this wave?
3 intervals
A=3x2 = 6 V
Horizontal interval = 5ms Vertical interval = 2 V
3 intervalsA=3x2V = 6 V
4 intervalsT=4x5ms = 20 ms
The frequency of a wave (in Hz or s-1) is related to it’s period (s) in a simple way:
Pro-tip – Sometimes in larger exam problems you’ll be given the Period and you’ll need Frequency to complete the question. That’s where this equation is very handy.
𝑓 =1
𝑇or 𝑇 =
1
𝑓
Dr Pusey’s plays a sick “D” note on his guitar with a frequency of 440 Hz. How many mad air wave-fronts hit the audience every second?
How many seconds between each Wavefront?
Dr Pusey plays a sick “D” note on his guitar with a frequency of 440 Hz. How many mad air wave-fronts hit the audience every second? Answer: 440 mad wave-fronts
How many seconds between each Wavefront?
Answer = 𝑻 =𝟏
𝒇=
𝟏
𝟒𝟒𝟎= 0.0023 s
= 2.3 ms
Dr Pusey is an awesome surfer (ok, not really). The seabreeze website indicates a swell period of 12 seconds. What is the frequency of the swell?
Dr Pusey is an awesome surfer (ok, not really). The seabreeze website indicates a swell period of 12 seconds. What is the frequency of the swell?
Answer = 𝒇 =𝟏
𝑻=
𝟏
𝟏𝟐= 0.083 Hz
Horizontal interval = 5ms Vertical interval = 2 V
What is the frequency of this wave?
4 intervalsT=4x5ms
= 20 ms
Horizontal interval = 5ms Vertical interval = 2 V
Now, Draw a wave with lower amplitude and higher frequency
4 intervalsT=4x5ms
= 20 ms
𝒇 =𝟏
𝑻
=𝟏
𝟎. 𝟎𝟐𝟎
= 𝟓𝟎 𝑯𝒛
Horizontal interval = 5ms Vertical interval = 2 V
If these two sets of sound waves were captured by a microphone, how would they sound different?
If these two sets of sound waves were captured by a microphone, how would they sound different?
Answer: The blue wave would sound louder and have a lower pitch than the red wave
The product of the frequency (f)and wavelength (λ) is the wave velocity (v)
Examples of wave velocities:
Sound waves in air: 340 m/s
Light waves in a vacuum: 3x108 m/s
𝑣 = 𝑓𝜆 or 𝑓 =𝑣
𝜆𝜆 =
𝑣
𝑓or
What is the wavelength of the ‘D’ note with a frequency of 440 Hz as it gets blasted across the air to Dr Pusey’s Guitar audience?
What is the wavelength of the ‘D’ note with a frequency of 440 Hz as it gets blasted across the air to Dr Pusey’s Guitar audience?
𝜆 =𝑣
𝑓=340𝑚/𝑠
440 /𝑠= 0.77m
When surfing a huge 12s wave, Dr Pusey’s GPS watch tells him he’s travelling at 4.0 m/s towards shore. How far away is the next wave?
When surfing a huge 12s wave, Dr Pusey’s GPS watch tells him he’s travelling at 4.0 m/s towards shore. How far away is the next wave?
𝜆 =𝑣
𝑓=
𝑣
1𝑇
=4.0𝑚/𝑠
112𝑠
= (12𝑠)(4𝑚/𝑠) = 48m
The audible range of frequencies for a healthy human is from 20 Hz to 20 kHz. What range of wavelengths in air do these frequencies correspond to?
The audible range of frequencies for a healthy human is from 20 Hz to 20 kHz. What range of wavelengths in air do these frequencies correspond to?
𝜆𝑚𝑖𝑛 =340
20=160m
𝜆𝑚𝑎𝑥 =340
20000=0.160m = 16cm
How did you go?Recall the major characteristics of a wave
Frequency
Amplitude
Wavelength
Speed
Read and draw wave graphs
Demonstrate an understanding of the relationships between frequency, period, wavelength and wave speed.
Perform calculations using the equations:
𝑣 = 𝑓𝜆
𝑓 =1
𝑇
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