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Sean_Sylvester1 wrote:

Tom_MS wrote:

Sean_Sylvester1 wrote:
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

Tom_MS wrote:

Sean_Sylvester1 wrote:

Tom_MS wrote: 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.

Sean_Sylvester1 wrote:

Tom_MS wrote:

Sean_Sylvester1 wrote:
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

Sean_Sylvester1 wrote: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

Tom_MS wrote:

Sean_Sylvester1 wrote: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.

Sean_Sylvester1 wrote:Correct! Your turn

Tom_MS wrote: 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?

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.

jkang wrote:

Tom_MS wrote: 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. (Click to Show Hidden Text)

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.