Optics B/C

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Adi1008
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Re: Optics B/C

Postby Adi1008 » March 15th, 2017, 3:36 pm

What is the smallest time delay required between two waves of 400nm light to obtain complete destructive interference?
You can answer I just wanted to give it a shot.
I'm getting...
6.67*10^-16 seconds. This is using the distance over time definition of the speed of light with a 200nm distance to create fully destructive interference.
That's correct; your turn!
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Re: Optics B/C

Postby Tom_MS » March 17th, 2017, 8:20 am

That's correct; your turn!
A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.

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Re: Optics B/C

Postby Sean_Sylvester1 » March 19th, 2017, 11:07 am

That's correct; your turn!
A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.
Using the lensmakers formula and its derivation for thick lenses, I came up with an answer of 13.42 diopters
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Re: Optics B/C

Postby Tom_MS » March 19th, 2017, 2:54 pm

That's correct; your turn!
A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.
Using the lensmakers formula and its derivation for thick lenses, I came up with an answer of 13.42 diopters
Almost. To find the front vertex power you need to subtract the equivalent focal length by the distance from the front of the lens to the first principal plane.

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Re: Optics B/C

Postby Sean_Sylvester1 » March 19th, 2017, 4:38 pm

A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.
Using the lensmakers formula and its derivation for thick lenses, I came up with an answer of 13.42 diopters
Almost. To find the front vertex power you need to subtract the equivalent focal length by the distance from the front of the lens to the first principal plane.
Is it 64 diopters then? Since the equivalent focal length is the inverse of power and then subtract .09 from that
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Re: Optics B/C

Postby Tom_MS » March 19th, 2017, 6:34 pm


Using the lensmakers formula and its derivation for thick lenses, I came up with an answer of 13.42 diopters
Almost. To find the front vertex power you need to subtract the equivalent focal length by the distance from the front of the lens to the first principal plane.
Is it 64 diopters then? Since the equivalent focal length is the inverse of power and then subtract .09 from that
Keep in mind that the front surface radius will not be the same as the distance to the principal plane.

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Re: Optics B/C

Postby Sean_Sylvester1 » March 19th, 2017, 7:45 pm

Almost. To find the front vertex power you need to subtract the equivalent focal length by the distance from the front of the lens to the first principal plane.
Is it 64 diopters then? Since the equivalent focal length is the inverse of power and then subtract .09 from that
Keep in mind that the front surface radius will not be the same as the distance to the principal plane.
okay, so I think it would be 80.55 diopters since the power of lens 1 is 5.55 m^-1 and P2 is 12.5 m^-1 so
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Re: Optics B/C

Postby Tom_MS » March 20th, 2017, 3:11 am


Is it 64 diopters then? Since the equivalent focal length is the inverse of power and then subtract .09 from that
Keep in mind that the front surface radius will not be the same as the distance to the principal plane.
okay, so I think it would be 80.55 diopters since the power of lens 1 is 5.55 m^-1 and P2 is 12.5 m^-1 so
Nice! Your turn

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Re: Optics B/C

Postby Sean_Sylvester1 » March 21st, 2017, 6:54 pm

Alright so here's a quick conceptual question. You have a converging lens and divide the face into 4 equally sized areas. You then try to project an image using the lens. What happens when you place a piece of paper over quadrant 1,2,3 and 4. How about just 1 and 2 , or 1 and 4
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Re: Optics B/C

Postby Sean_Sylvester1 » March 21st, 2017, 6:59 pm

correction I meant to say concave mirror
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Re: Optics B/C

Postby Tom_MS » March 21st, 2017, 7:47 pm

Alright so here's a quick conceptual question. You have a converging lens and divide the face into 4 equally sized areas. You then try to project an image using the lens. What happens when you place a piece of paper over quadrant 1,2,3 and 4. How about just 1 and 2 , or 1 and 4
Using the principle that all light coming from a point gets focused to the same point (no matter where it reflects), it would make sense that the image would grow a bit dimmer whenever one part of it gets covered. When two parts are covered, it is dimmed more.

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Re: Optics B/C

Postby Sean_Sylvester1 » March 23rd, 2017, 5:29 am

Alright so here's a quick conceptual question. You have a converging lens and divide the face into 4 equally sized areas. You then try to project an image using the lens. What happens when you place a piece of paper over quadrant 1,2,3 and 4. How about just 1 and 2 , or 1 and 4
Using the principle that all light coming from a point gets focused to the same point (no matter where it reflects), it would make sense that the image would grow a bit dimmer whenever one part of it gets covered. When two parts are covered, it is dimmed more.
Correct! Your turn
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Re: Optics B/C

Postby Tom_MS » March 31st, 2017, 8:25 am

Correct! Your turn
Polarized light of intensity I strikes a rotating polarizing film whose angle is given by arcsin(1/t) where t is time in seconds. At one time does exactly 25% of the initial intensity of the polarized light get through the film?

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Re: Optics B/C

Postby jkang » April 3rd, 2017, 9:05 am

Polarized light of intensity I strikes a rotating polarizing film whose angle is given by arcsin(1/t) where t is time in seconds. At one time does exactly 25% of the initial intensity of the polarized light get through the film?
No one's tried in a while, so let me.
Malus' law states I = I0cos(x). In this case, 0.25=1*cos(arcsin(1/t))^2. Solving the expression for a positive t, we find t=1.1547 seconds.
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Re: Optics B/C

Postby Tom_MS » April 3rd, 2017, 10:04 am

Polarized light of intensity I strikes a rotating polarizing film whose angle is given by arcsin(1/t) where t is time in seconds. At one time does exactly 25% of the initial intensity of the polarized light get through the film?
No one's tried in a while, so let me.
Malus' law states I = I0cos(x). In this case, 0.25=1*cos(arcsin(1/t))^2. Solving the expression for a positive t, we find t=1.1547 seconds.
Correct. Your turn.


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