Optics B/C

Test your knowledge of various Science Olympiad events.
Pettywap
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Re: Optics B/C

Postby Pettywap » February 11th, 2018, 4:28 am

A pair of ideal polarizing filters are placed one in front of the other near a source of light so that the rays arrive perpendicular to the planes of the filters. What angle should the polarization axes be placed so that the second filter transmits 0.25 of the light energy it receives?
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Re: Optics B/C

Postby UTF-8 U+6211 U+662F » February 11th, 2018, 9:10 am

A pair of ideal polarizing filters are placed one in front of the other near a source of light so that the rays arrive perpendicular to the planes of the filters. What angle should the polarization axes be placed so that the second filter transmits 0.25 of the light energy it receives?
[math]\cos^2 \theta = \frac14; \cos \theta = \frac12; \theta = \frac\pi3 = 60 \degree.[/math]

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Re: Optics B/C

Postby Pettywap » February 11th, 2018, 3:07 pm

A pair of ideal polarizing filters are placed one in front of the other near a source of light so that the rays arrive perpendicular to the planes of the filters. What angle should the polarization axes be placed so that the second filter transmits 0.25 of the light energy it receives?
[math]\cos^2 \theta = \frac14; \cos \theta = \frac12; \theta = \frac\pi3 = 60 \degree.[/math]
Correct!! your turn
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Re: Optics B/C

Postby UTF-8 U+6211 U+662F » February 11th, 2018, 3:44 pm

A converging lens in air is placed underwater. What happens to the lens?

Hint: Be careful.

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Re: Optics B/C

Postby chopchpp » February 11th, 2018, 4:33 pm

A converging lens in air is placed underwater. What happens to the lens?

Hint: Be careful.
focal length increases?

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Re: Optics B/C

Postby UTF-8 U+6211 U+662F » February 11th, 2018, 4:47 pm

A converging lens in air is placed underwater. What happens to the lens?

Hint: Be careful.
focal length increases?
There's more to the correct answer.

Hint 2: I didn't specify what the lens was made out of.

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Re: Optics B/C

Postby Pettywap » February 11th, 2018, 6:19 pm

A converging lens in air is placed underwater. What happens to the lens?

Hint: Be careful.
focal length increases?
There's more to the correct answer.

Hint 2: I didn't specify what the lens was made out of.
It also depends on the index of refraction of the lens. The focal length could be infinity because the converging lens could be the same material as water, which means there is no refraction.
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Re: Optics B/C

Postby UTF-8 U+6211 U+662F » February 11th, 2018, 6:24 pm

Almost there, a little more to the answer.

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Re: Optics B/C

Postby UTF-8 U+6211 U+662F » February 19th, 2018, 10:05 am

All right, my question killed the marathon, so I'll just post the answer.
If the refractive index of the lens > 1.33: The focal length increases.
If the refractive index of the lens = 1.33: The lens becomes invisible.
If the refractive index of the lens < 1.33: The lens becomes diverging.
1) Fill in the blank: Stars moving toward us appear more _ (color).
2) Why is this?

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Re: Optics B/C

Postby jonboyage » February 19th, 2018, 10:48 am

All right, my question killed the marathon, so I'll just post the answer.
If the refractive index of the lens > 1.33: The focal length increases.
If the refractive index of the lens = 1.33: The lens becomes invisible.
If the refractive index of the lens < 1.33: The lens becomes diverging.
1) Fill in the blank: Stars moving toward us appear more _ (color).
2) Why is this?
Blue; wavelength decreases due to Doppler shift
I was in a bin

Rustin '19
UPenn '23


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