Optics B/C

ChingCL
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Re: Optics B/C

Postby ChingCL » April 17th, 2017, 1:26 pm

The info I posted previously was about LSS specifically for mounting a laser for adjustment. People may use the LSS Laser mount ... .stl for 3D print and create a simple deign of their own Laser Head Locator for custom fit of their 14 mm OD laser. I did not discuss about LS.

One of the Div B students I coached was willing spend significant amount of time to create templates for LS. I can offer all of the tips I suggested:
1. Keep the total distance between the first mirror and the last mirror as short as practical.
2. Keep the total distance between the first mirror and the target as short as practical.
3. Use small angles of incidence as much as practical so that the laser beam has more chance to hit a mirror and the refraction effect is less (45 deg is O.K., 30 deg is much better than 70 deg).
4. Combine a few mirrors together as a template (or a partial template).
5. Allow one or two (not 5) mirrors for adjustment (the rest would be "fixed" to the template) so that angular errors would be reduced.
6. Consider the effects of refraction and mirror thickness (note: mirror thickness is unknown) in the template. Note: Some mirror arrangements can partially cancel the refraction effect.
7. Consider many possible positions of the stationary mirror and barriers (Div C) and prepare various templates for various situations. Note: It is difficult to be complete.
8. Consider a backup plan to drop one mirror so that you can still comfortably use 5 mirrors to hit the target (within 2? cm).

Good luck to your LS!

Avogadro
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Re: Optics B/C

Postby Avogadro » April 17th, 2017, 4:41 pm

It's funny the difference a typo can make- I did indeed mean the LSS, apparently I just missed one S, sorry! :P I was referring to the issue that taping a laser pointer to the table does not make for a very suitable method of mounting.
Lower Merion 2017
Subtitled: Revenge of the Non-Harriton

Placement Record:

Code: Islip | Conestoga | Tiger | Regionals | States
Out of: 61 | 42 | 36 | 37 | 36

Chemistry Lab: 9 | - | - | 4 | 4
Astronomy: 14 | - | 5 | 10 | 3
Material Science: 12 | 19 | 9 | 5 | 9
Optics: 14 | 7 | 3 | 4 | 2

ChingCL
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Re: Optics B/C

Postby ChingCL » April 17th, 2017, 8:14 pm

It's funny the difference a typo can make- I did indeed mean the LSS, apparently I just missed one S, sorry! :P I was referring to the issue that taping a laser pointer to the table does not make for a very suitable method of mounting.
No problem! I hope at least one or two of those tips for LS would be useful to you and others.

As far as mounting the laser goes, although a 3D printed part is nice, you can do without. Securing one end at the LSS frame (reasonably tight fit but allow some angular movement) while making the other end somewhat adjustable is a good way to go. The other end should be as far apart from the first end as practical. You can take a small piece of wood and drill a hole slightly (2 mm?) larger than the diameter of the laser. Also cut out a notch to accommodate the power button of the laser if needed. Tape the OD of the laser so that it fits at about the center of the hole on the small piece of wood. Adjusting the laser beam to the center of the back wall while glueing the wood piece in space with three (one at a time if that's easier) bass or hard wood sticks (about 1/4" size). Take out the laser and tape. Add tape or epoxy at the location where needed or just simply shim the laser so that the laser beam will hit the center of the back wall.

kenniky
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Re: Optics B/C

Postby kenniky » April 24th, 2017, 12:04 pm

Having trouble finding stuff on dispersion... here are some sample questions that I literally can't find sources for

Boyceville 23. Rank the following media in terms of the variation of dispersion; rank from (1) the greatest variation to (4) the least variation.

Crown glass; Flint glass; Fused quartz; Quartz
1 Flint glass
2 Quartz
3 Crown glass
4 Fused quartz
Wright State 10. What is the index of refraction for an equilateral prism with a minimum dispersion angle of 30 degrees?

a. 1.50 b. 1.52 c. 1.58 d. 1.62
d. 1.62
Any help would be greatly appreciated

Thanks!!!!
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Re: Optics B/C

Postby Crtomir » April 27th, 2017, 8:28 am

Wright State 10. What is the index of refraction for an equilateral prism with a minimum dispersion angle of 30 degrees?

a. 1.50 b. 1.52 c. 1.58 d. 1.62
d. 1.62
I'm guessing that something is wrong with the answer. The formula for index of refraction of a prism with internal angle A and minimum angle of deviation (not dispersion) D is given by:

n = sin( (A+D)/2 ) / sin( A/2 )

In this case, A = 60 deg. (equilateral triangle) and D = 30 deg., so

n = sin( (60 + 30)/2 ) / sin( 60/2 ) = sin( 45 ) / sin( 30 ) = 1.41

However, this answer is not one of those listed above. Not sure if the answer key was wrong or the test was written wrong. Since the test says "dispersion" instead of "deviation", I'm guessing the test was wrong. Dispersion is the separation at different wavelengths, but deviation is the angle between the beam incident to a prism and the light exiting the prism on the other side (at a SINGLE wavelength). Therefore, you only get the index of refraction at that SINGLE wavelength.

A useful bit of information on this can be found here: https://www.cis.rit.edu/class/simg232/l ... ersion.pdf

Or here: http://hyperphysics.phy-astr.gsu.edu/hb ... prism.html

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Re: Optics B/C

Postby kenniky » April 27th, 2017, 10:39 am

Wright State 10. What is the index of refraction for an equilateral prism with a minimum dispersion angle of 30 degrees?

a. 1.50 b. 1.52 c. 1.58 d. 1.62
d. 1.62
I'm guessing that something is wrong with the answer. The formula for index of refraction of a prism with internal angle A and minimum angle of deviation (not dispersion) D is given by:

n = sin( (A+D)/2 ) / sin( A/2 )

In this case, A = 60 deg. (equilateral triangle) and D = 30 deg., so

n = sin( (60 + 30)/2 ) / sin( 60/2 ) = sin( 45 ) / sin( 30 ) = 1.41

However, this answer is not one of those listed above. Not sure if the answer key was wrong or the test was written wrong. Since the test says "dispersion" instead of "deviation", I'm guessing the test was wrong. Dispersion is the separation at different wavelengths, but deviation is the angle between the beam incident to a prism and the light exiting the prism on the other side (at a SINGLE wavelength). Therefore, you only get the index of refraction at that SINGLE wavelength.

A useful bit of information on this can be found here: https://www.cis.rit.edu/class/simg232/l ... ersion.pdf

Or here: http://hyperphysics.phy-astr.gsu.edu/hb ... prism.html
You see that's what I thought too, but the fact that both the question and the answers are wrong leads me to think otherwise :p
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Re: Optics B/C

Postby Crtomir » April 27th, 2017, 11:32 am

Wright State 10. What is the index of refraction for an equilateral prism with a minimum dispersion angle of 30 degrees?

a. 1.50 b. 1.52 c. 1.58 d. 1.62
d. 1.62
I'm guessing that something is wrong with the answer. The formula for index of refraction of a prism with internal angle A and minimum angle of deviation (not dispersion) D is given by:

n = sin( (A+D)/2 ) / sin( A/2 )

In this case, A = 60 deg. (equilateral triangle) and D = 30 deg., so

n = sin( (60 + 30)/2 ) / sin( 60/2 ) = sin( 45 ) / sin( 30 ) = 1.41

However, this answer is not one of those listed above. Not sure if the answer key was wrong or the test was written wrong. Since the test says "dispersion" instead of "deviation", I'm guessing the test was wrong. Dispersion is the separation at different wavelengths, but deviation is the angle between the beam incident to a prism and the light exiting the prism on the other side (at a SINGLE wavelength). Therefore, you only get the index of refraction at that SINGLE wavelength.

A useful bit of information on this can be found here: https://www.cis.rit.edu/class/simg232/l ... ersion.pdf

Or here: http://hyperphysics.phy-astr.gsu.edu/hb ... prism.html
You see that's what I thought too, but the fact that both the question and the answers are wrong leads me to think otherwise :p
Event supervisors often make mistakes. I know, because I've made plenty myself. Sometimes, if we catch the mistake early enough, we can ignore that problem in the grading.

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Re: Optics B/C

Postby DrKoolKat » May 2nd, 2017, 4:03 pm

On the test exchange, I found Optics C nationals test from 2011 under resources for Optics B. Was the 2011 Optics B nationals test ever released? If it was, where could I find it? Also, for the energy of a photon (E=hf) E is energy in joules, h is Planck's Constant, and f is frequency, what unit is frequency in?

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Re: Optics B/C

Postby kenniky » May 2nd, 2017, 9:28 pm

On the test exchange, I found Optics C nationals test from 2011 under resources for Optics B. Was the 2011 Optics B nationals test ever released? If it was, where could I find it? Also, for the energy of a photon (E=hf) E is energy in joules, h is Planck's Constant, and f is frequency, what unit is frequency in?
Frequency is in Hz, or 1/s I believe (if you're using 6.626 * 10^-34 for h)
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Re: Optics B/C

Postby DrKoolKat » May 3rd, 2017, 1:38 pm

On the test exchange, I found Optics C nationals test from 2011 under resources for Optics B. Was the 2011 Optics B nationals test ever released? If it was, where could I find it? Also, for the energy of a photon (E=hf) E is energy in joules, h is Planck's Constant, and f is frequency, what unit is frequency in?
Frequency is in Hz, or 1/s I believe (if you're using 6.626 * 10^-34 for h)
Thank you for the clarification


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