(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A small homemade ﬁrework goes oﬀ 3 meters about the surface of the water where a person is diving. The diver is 10 meters below the surface of the water.

(a). How much time passes from the instant the ﬁrework goes oﬀ until the diver sees it?

(b). How much time passes from the instant the ﬁrework goes oﬀ until the diver hears it?

When the ﬁrework goes oﬀ, another individual is traveling on a boat moving at a speed of

30 km per hour away from the ﬁrework. That person is standing on the upper deck of the

boat, also 3 m above the surface.

(c). If the person on the boat hears a sound with frequency 200 Hz, what is the actual

frequency of the ﬁrework’s sound?

(d). If the frequency of the light emitted by the ﬁreworks is 5 × 10^14 Hz, what is the

wavelength of this light as seen by the diver?

2. Relevant equations

Formula A : Velocity = Wavelength (gamma) * Frequency ( we can change this around too)

Formula B : Frequency (receding sound) = (1- V(not)/V)*F(not)

3. The attempt at a solution

For beginners, I have no idea how to successfully start, or complete A. & B. (need help)

I however completed C & D and I'm hoping I completed them correctly :

For part C : We use Formula B and heres my setup for this:

(1 - (3.6*10^6(m/s))/(343(m/s)))*200hz = -2.1*10^6 hz

^^Seems very high but i had to convert the speed of the boat from 30 Kilometers per hour to meters per second.

For Part D : We use Formula A and heres my setup :

Wavelength (gamma) = Velocity / Frequency : 3 * 10^8 (speed of light) / 5*10^14 (hz) = 6 * 10^-7 .

^^Very small wavelength. I have no way of checking my answers so I ask please review this and give the best advice. As always, thank you for reviewing my work and hopefully i will get some much needed help with parts A & B.

Very Respectfully,

UMDstudent

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# Homework Help: Frequency, Time, Wavelength = Doppler Effect

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