TBR, Physics, Light, Passage 2 # 11

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Sammy1024

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11. For parallel rays of white light incident on a spherical mirror, the light's color components have focal lengths that:

I was just wondering how this would direct me towards thinking about reflection? I know reflection is independent of frequency and blah but didn't know how the question would have made me think of reflection. Is it where it says "light incident"?

Choice A is the best answer. The law of reflection states that the angle of incidence is equal to the angle of reflection. This law is independent of the frequency (and wavelength) of the incident light and independent of the refractive index of the material of which the mirror is made. The best answer is choice A.

12. If a lens is immersed in water, then the medium surrounding the lens has a higher index of refraction, which results in less bending of the light rays.

Isn't it supposed to be the opposite? Doesn't light bend more when it goes from lower to higher n value?
 
I'm not sure about 11, but for #12 when you immerse a lens in water, the difference between the indices of refraction of the lens and the medium becomes smaller (the lens refracts light at a smaller angle). A higher difference in the indices of refraction allows for a greater bending of light.
I hope that was as clear as it sounds in my head.
 
Oh!!! Like when is says less bending of light rays, they mean less bending away from the normal line??
 
For 11 it seems like it's process of elimination. It should't make you think of reflection, rather the other answer choices are just wrong in some way. Answer A is true even though it does't have to do with focal length. A spherical mirror won't really have a focal length because all of the rays are divergent off of its surface.

Oh!!! Like when is says less bending of light rays, they mean less bending away from the normal line??

My explantation is based on the figure (http://en.wikipedia.org/wiki/Snell's_law).

When they say water has a higher index they mean relative to air.

When you increase the refractive index of the incident light material (water 1.3 vs. air ~1), theta 2 will increase. In other words the light won't bend as much. In both cases you are going from a lower to higher value. Water to lens is just a smaller index differential so it won't bend as much.

Air (sin 30)(1) = (sin theta)(2) Lens

theta = ~14

Water (sin30)(1.3) = (sin theta)(2) Lens

theta = ~19
 
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And then did you just randomly pick 2 to just plug it in the equation?

Otherwise, I get it. I thought the answer was saying that it was going from air to water, but it would bend less when it entered water. Even though it would bend more once it entered water.
 
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