electromagnetic waves, doppler effect


by lovelyrwwr
Tags: doppler, effect, electromagnetic, waves
lovelyrwwr
lovelyrwwr is offline
#1
Mar23-13, 01:32 PM
P: 48
I pay for chegg to help me with physics but sometimes I'm not quite sure if the site is right. Could you please tell me if I am doing the below problem correctly? My way is different than Chegg's so I would just like to make sure I am not wrong because I am getting different answer than that site :) Thank you!

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he drawing shows three situations—A, B, and C—in which an observer and a source of electromagnetic waves are moving along the same line. In each case the source emits a wave that has a frequency of . The arrows in each situation denote velocity vectors of the observer and source relative to the ground and have the magnitudes indicated (v or ), where the speed v is . Calculate the observed frequency in each of the three cases.



2. Relevant equations
fo = fs(1 + - Vr/C)
Vr = 1.5E6 m/s
fs 4.57E14

3. The attempt at a solution
a.
here it is relative velocity is just Vr and it is a (-) sign because the faster object is outpacing the slower object and thus they are receding from one another or moving away
fo =(4.57E14)(1 - 1.5E6/3E8)
fo = 4.55E14 hz

b.
here relative velocity is 3Vr and it is a minus sign because the objects are moving away from one another
fo =(4.57E14)(1 - 3*1.5E6/3E8)
fo = 4.501E14 hz

c.

here it is 2Vr and a + sign because the objects are moving towards each other

fo = (4.57E14)(1 + 2*1.5E6/3E8)
fo = 4.62E14 hz
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TSny
TSny is offline
#2
Mar23-13, 01:51 PM
HW Helper
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P: 4,482
Quote Quote by lovelyrwwr View Post
fo = fs(1 + - Vr/C)
Vr = 1.5E6 m/s
fs 4.57E14

3. The attempt at a solution
a.
here it is relative velocity is just Vr and it is a (-) sign because the faster object is outpacing the slower object and thus they are receding from one another or moving away
fo =(4.57E14)(1 - 1.5E6/3E8)
fo = 4.57E14 hz

b.
here relative velocity is 3Vr and it is a minus sign because the objects are moving away from one another
fo =(4.57E14)(1 - 3*1.5E6/3E8)
fo = 4.52E14 hz
For parts a and b it looks to me that you have it set up correctly but you're off a bit in the evaluation. I get different answers for the third digit. I think your answer to part c is correct.
lovelyrwwr
lovelyrwwr is offline
#3
Mar23-13, 02:07 PM
P: 48
whoops edited. thank you so much!


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