# Physics Optics Review

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#### chandler742

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When yellow light moves from air to water i.e. n air<n h2o

Does the transmitted electromagnetic wave change color in the water?

A) Yes. EM light waves move slower in a material with
a higher index of refraction, and since wavelength
and speed of light is directly proporational, there will be
shift to a smaller wavelength i.e. blue shift

B) Yes. EM light waves move slower in a material with
a higher index of refraction, and since frequency
and speed of light is directly proportional, there will be a
shift to a smaller frequency i.e. red shift

C) No. EM light waves move slower in a material with
a higher index, however color of light is a property of
EM wave's frequency. and frequency stays constant
regardless of n.

D) No. EM light waves move slower in a material with
a higher index, however color of light is a property
of EM wave's wavelength, and wavelength stays
constant regardless of n.

#### freakazoid

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C). Frequency does not change when going from medium to medium, though speed might at a cost to wavelength . . .

#### phatty925

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how come color of light is a property of EM wave's FREQUENCY and not the wavelength? i thought the longer the wavelength, closer the color is to red on spectrum and shorter the wavelength, closer the color is to violet. i understand frequency doesn't change with a change in medium, but is color of light a property of frequency?

#### Mr. Z

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the answer is A. when light enters a medium with a higher index of refraction the wavelength gets shorter, the frequency remains the same. Shorter wavelength would be a blue shift

#### surge

##### Medicinski Znanstvenik
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Mr. Z is correct.

#### Mr. Z

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here's one:

"the effects of two or more waves on the displacement of a particle are independant" is a statement of:

a) Interference
b) Huygen's principle
c) Superposition
d) all of the above

#### freakazoid

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Whoops. Good call.

Let me try again. C?? (For Mr. Z's question)

#### chandler742

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Great Job, Freakazoid.

The answer is indeed C. I am impressed. The color of a wave in 400-700 nm range in the electromagnetic spectrum is attributed to its Frequency not wavelength. I agree that the wavelength decreases, however COLOR IS A PROPERTY OF FREQUENCY.

Also the frequency of a wave not the wavelength activates the cones in the retina.

Here is an easy one. When white light enters a prism and then exits, dispersion occurs. So, what color light gets bended the least in reference to the normal?

A. Red
B. Yellow
C. Green
D. Violet

#### surge

##### Medicinski Znanstvenik
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Is it D - Violet?
(I'm assuming the prism is made of regular, colorless glass)

Would it be generally true that shorter wavelengths bend less?

Also, about your previous question... I always heard the color being attributed to wavelength. Obviously the wavelength and frequency are related.... Where can I find more on this?

#### Focus

##### crazy!!
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Hi Surge,

Frequency of a wave never changes going from one medium to another, from what I understand. So chandler's question has to do with wavelength.

You can immediately eliminate B and C, as they are not extremes. So it's A or D.

Look at the two option's wavelengths, then relate it with the equation:

n * sin X = n2 * sinX2

Remember that N = C/V

Where C is speed of light, V is velocity.

and V = WAVELENGTH x frequency.

- Focus

#### freakazoid

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I would pick A.

The higher the frequency, the slower it goes.

Based on n=c/v,

violet would have the greatest index of refraction
while red would have the smallest.

since n(violet)*sin(theta) = n(red)*sin(theta2)

And n(violet) > n(red)
Then theta < theta2

Meaning that while violet has the smallest angle in reference to the normal, it is bent the most because if the light was transmitted from one medium to another medium with the same index of refraction, it would have the same angle, meaning that the smaller the angle, and greater the "bending".

#### Mr. Z

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the answer to the question i posted is C.

#### phatty925

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what is superposition??

#### chandler742

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the answer is red light gets bended least in reference to the normal. The reason is that shorter wavelengths "sense" a higher index of refraction, thus it moves further away from the normal.

white light is separated to its components ala a rainbow.

P.S. if you have a pink floyd CD/record cover you will notice a
prism and white light separated according to its componets.

#### Mr. Z

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when any two waves overlap, the actual displacement of any point on the string, at any time, is obtained by adding the displacement that only the first wave would have and the displacement that only the second wave would have. This is the principle of superposition.

Overlapping waves can be said to experience interference, which can be either constructive (amplitude increases) or destructive (amplitude decreases).