course Phy 202
7/7 12:20am
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Question: `qPrinciples of Physics and General College Physics 23.28 A light beam exits the water surface at 66 degrees to vertical. At what angle was it incident from under the water?
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Your solution:
The angle is incident at that same angle, 66 degrees. I think this because the angle of incidence is the angle perpendicular to the surface. Since this surface is water, it is a straight surface and the angle carries on under water.
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Given Solution:
`a****
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Self-critique (if necessary):
Ok?
That solution was missing. I've just filled it in:
The angle of incidence and the angle of refraction are both measured relative to the normal direction, i.e., to the direction which is perpendicular to the surface. For a horizontal water surface, these angles will therefore be measured relative to the vertical.
66 degrees is therefore the angle of refraction.
Using 1.3 as the index of refraction of water and 1 as the index of refraction of air, we would get
sin(angle of incidence) / sin(angle of refraction) = 1.3 / 1 = .7, very approximately, so that
sin(angle of incidence) = 1.3 * sin(angle of refraction) = .7 * sin(66 deg) = .7 * .9 = .6, very approximately, so that
angle of incidence = arcSin(.6) = 37 degrees, again a very approximate result.
You should of course use a more accurate value for the index of refraction and calculate your results to at least two significant figures.
Self-critique Rating:
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Question: `qPrinciples of Physics and General College Physics 23.46 What is the power of a 20.5 cm lens? What is the focal length of a -6.25 diopter lens? Are these lenses converging or diverging?
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Your solution:
The equation we have to work with is
Focal length= 1/length
FL1= 1/.205 m
FL1= 4.87 m
Because the focal length is positive, this is a converging lens
FL2= 1/-6.25 m
FL2= -.16 m
Because the focal length is negative, this is a diverging lens
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Given Solution:
`aThe power of the 20.5 cm lens is 1 / (.205 meters) = 4.87 m^-1 = 4.87 diopters.
A positive focal length implies a converging lens, so this lens is converging.
A lens with power -6.25 diopters has focal length 1 / (-6.25 m^-1) = -.16 m = -16 cm.
The negative focal length implies a diverging lens.
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Self-critique (if necessary):
ok
Self-critique Rating:
3
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Question: `qquery gen phy problem 23.32 incident at 45 deg to equilateral prism, n = 1.52; and what angle does light emerge?
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Your solution:
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That last problem was included in the document. You should show your solution then self-critique.
&#See my notes and let me know if you have questions. &#