## Optics B/C

blue cobra
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### Re: Optics B/C

I can't seem to get the hang of Doppler effect problems. Could someone please guide me through an example?
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### Re: Optics B/C

All right. Say you have this problem:
A train is moving directly towards you at 2×108 m/s. The (monochromatic) light on the front of the train has a wavelength of 250 nanometers in the frame of the train. What wavelength do you observe?

I will post answer and how-to-solve later, because there are...ah...things on my computer that are preventing me from doing that at present moment. I would like you to try your hand at solving it first, anyhow.

Equation (if it shows up right): $\frac{f_s}{f_o} = \sqrt{\frac{1+\beta}{1-\beta}}$

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hexagonaria
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### Re: Optics B/C

Schedule conflict.. Goodbye optics
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### Re: Optics B/C

Is there a difference between red glass and a red filter? Essentially, does red glass filter red light in the same way that a filter would. I know stained glass would but I am not sure about the more general term glass.. I hope I made that question clear enough to understand.
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SciBomb97
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### Re: Optics B/C

Well, I think it's that red glass reflects and transmits only red light, and a red filter just takes the red wavelengths of light in the light that passes through it.
That reminds me of the emission/absorption spectrum thing.
hexagonaria wrote:Schedule conflict.. Goodbye optics
Me too, and if we make it to nationals, it conflicts with the same event at nationals too...
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foreverphysics
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### Re: Optics B/C

I'm screwed. My partner knows nothing. So, so, so screwed...

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blue cobra
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### Re: Optics B/C

foreverphysics wrote:All right. Say you have this problem:
A train is moving directly towards you at 2×108 m/s. The (monochromatic) light on the front of the train has a wavelength of 250 nanometers in the frame of the train. What wavelength do you observe?

I will post answer and how-to-solve later, because there are...ah...things on my computer that are preventing me from doing that at present moment. I would like you to try your hand at solving it first, anyhow.

Equation (if it shows up right): $\frac{f_s}{f_o} = \sqrt{\frac{1+\beta}{1-\beta}}$
$\frac{f_s}{f_o} = \sqrt{\frac{1+\beta}{1-\beta}}$

$f_o=\frac{f_s}{\sqrt{\frac{1+\beta}{1-\beta}}} \hspace{50} \beta=\frac{v}{c}$

$f_o=\frac{f_s}{\sqrt{\frac{1+\frac{v}{c}}{1-\frac{v}{c}}}} \hspace{50} f_s=\frac{c}{\lambda}$

$f_o=\frac{\frac{c}{\lambda}}{\sqrt{\frac{1+\frac{v}{c}}{1-\frac{v}{c}}}}$

$f_o=\frac{\frac{3*10^8}{250*10^{-9}}}{\sqrt{\frac{1+\frac{2*10^8}{3*10^8}}{1-\frac{2*10^8}{3*10^8}}}}$

$f_o=5.366563146*10^{14} s^{-1}$ or with sig figs

$f_o=5*10^{14} s^{-1}$

That's assuming I punched that beast into my calculator correctly
I knew that equation, but when I tried it out elsewhere I got the wrong answer. Is v positive or negative when the source is approaching? Either way I got the wrong answer on the example I did...
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chalker
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### Re: Optics B/C

SciBomb97 wrote:
hexagonaria wrote:Schedule conflict.. Goodbye optics
Me too, and if we make it to nationals, it conflicts with the same event at nationals too...
Which event is in conflict? We try to setup to schedule so events the same student is likely to compete in don't overlap (but obviously can't account for all possible overlaps)

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SciBomb97
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### Re: Optics B/C

chalker wrote:
SciBomb97 wrote:
hexagonaria wrote:Schedule conflict.. Goodbye optics
Me too, and if we make it to nationals, it conflicts with the same event at nationals too...
Which event is in conflict? We try to setup to schedule so events the same student is likely to compete in don't overlap (but obviously can't account for all possible overlaps)
For me, optics conflicts with microbe.
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himynameis
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### Re: Optics B/C

How would you go about writing the programs for a TI-84 calculator?

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