WEBVTT physics/ap-physics-1-2/fullerton
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Hi everyone and welcome back to educator.com.
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I am Dan Fullerton and in today's mini-lesson, we are going to talk about wave characteristics, specifically by going through page 1 of the APlusPhysics worksheet on wave characteristics, which you can find the link for down below.
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Now, again, note that these are not AP level questions, but they will test your basic understanding to see if we are at least in the ballpark of where we need to go.
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So let us dive into question 1.
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What is the wavelength of a 256 Hz sound wave in the air at standard temperature and pressure?
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For this set of questions, we are going to be asked to assume that the velocity of sound in air at standard temperature and pressure is 331 m/s.
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So what is the wavelength?
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Well if V = F(λ), then we know that λ wavelength = V/F or 331 m/s/256Hz = 1.29 meters, Answer Number 2.
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Number 2 -- The graph below represents the relationship between wavelength and frequency of waves created by two students shaking the ends of a loose spring.
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Calculate the speed of the waves generated in the spring.
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Well, we have a couple of different points we could use here, but all of these should follow our wave equation, V = F(λ), so I can solve here for (V) by picking a couple of points here.
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It looks like an easy point would be something like, frequency of 1 Hz and a wave length of 5 m, which would be 5 m/s.
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If I did that at any other point here on the curve too, this would be 2 × 2.5 or 5 or 2.5 × 2 or 5 or 5 × 1, again, is 5.
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We have the same speed everywhere, which we should expect.
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So our speed must be 5 m/s.
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Number 3 -- What is the period of a water wave if 4 complete waves pass a fixed point in 10 s?
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Well, period is the time it takes for one wave, so if we have 10 s for 4 waves, that would be 10/4 or 2.5 s per wave.
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The correct answer is Number 3.
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You could also do this by looking at frequency first.
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Frequency is the number of cycles per second and if you go through 10 cycles or 4 waves, over 10 s, you are going to get a frequency of 0.4 Hz, then period is 1 over frequency or 1/0.4 Hz, which again, is 2.5 s.
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However you want to get there, 2.5 s is your best answer.
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Number 4 -- If the frequency of a periodic wave is doubled the period of the wave will be...
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Well, period is 1 over frequency.
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If you double the frequency, you have divided the right hand side by 2 and you have to take half the periods, so the correct answer to 4 must be Number 1.
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Number 5 -- A 512 Hz sound wave travels 100 m to an observer through air at standard temperature and pressure.
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What is the wavelength of the sound wave?
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Well, V = F(λ)...
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...which implies that λ wavelength is going to be V/F or 331 m/s/512 Hz (frequency), which is just going to be about 0.65 m.
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Number 6 -- The diagram below represents a periodic wave.
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Which point on the wave is in phase with point (P)?
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So there is (P) -- in phase means it is the same point on a corresponding wave, so (P) and (C) would be in phase, so correct answer there is Number 3.
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Number 7 -- A periodic wave having a frequency of 5 Hz and a speed of 10 m/s, has what wavelength?
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Well, if V = F(λ), then λ = V/F, which is 10 m/s/5 Hz or just 2 m, so the correct answer there is Number 2.
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Two more -- Number 8 -- A ringing bell is located in a chamber.
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When the air is removed from the chamber, why can the bell be seen vibrating, but not heard?
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Well, light waves can travel through a vacuum, but sound waves cannot.
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Our last one -- The diagram below represents a transverse wave.
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The wavelength of the wave is equal to the distance between points.
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We need to find two same points on corresponding waves, so that would be (B) and (F) would work.
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That is one of our choices, Number 2, the distance between (B) and (F) would be 1 wavelength.
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All right, that concludes page 1 of the A+ Physics worksheet on wave characteristics.
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If this went well -- Excellent -- keep moving on to the higher level questions, the AP level questions.
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If it did not go so well, now would be a great time to go back and review wave characteristics.
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Thanks so much for your time everyone and have a great day.