light refraction

[cloak25]

If light passes from Medium A with an angle of incidence of 40° to the normal into Medium B with a refracted angle of 30° to the normal, what changes are observed in the speed and wavelength of the light in the two mediums?

A. It is faster and has a shorter wavelength in Medium A than in Medium B.
B. It is slower and has a shorter wavelength in Medium A than in Medium B.
C. It is faster and has a longer wavelength in Medium A than in Medium B.
D. It is slower and has a longer wavelength in Medium A than in Medium B.

So if the refracted angle is less than the incidence...doesn't that mean that medium B has a lower index of refraction and therefore less dense? Because when light goes from air (n = 1, less dense) to water (n = 1.33, more dense), it bends away from the normal. So in this case...its going from the more dense medium (since it starts from a medium with higher index of refraction?) to a less dense medium, therefore the index of refraction in medium B should be less than the index of refraction in medium A. So from the equations v=f x wavelength and n = c/v shouldn't the answer be B?.... obviously this is wrong and there is probably something I am missing...can someone offer their explanation to this question? thanks

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[Jepstein30]

If light passes from Medium A with an angle of incidence of 40° to the normal into Medium B with a refracted angle of 30° to the normal, what changes are observed in the speed and wavelength of the light in the two mediums?

A. It is faster and has a shorter wavelength in Medium A than in Medium B.
B. It is slower and has a shorter wavelength in Medium A than in Medium B.
C. It is faster and has a longer wavelength in Medium A than in Medium B.
D. It is slower and has a longer wavelength in Medium A than in Medium B.

So if the refracted angle is less than the incidence...doesn't that mean that medium B has a lower index of refraction and therefore less dense? Because when light goes from air (n = 1, less dense) to water (n = 1.33, more dense), it bends away from the normal. So in this case...its going from the more dense medium (since it starts from a medium with higher index of refraction?) to a less dense medium, therefore the index of refraction in medium B should be less than the index of refraction in medium A. So from the equations v=f x wavelength and n = c/v shouldn't the answer be B?.... obviously this is wrong and there is probably something I am missing...can someone offer their explanation to this question? thanks

Light bends more towards the normal so its going into a more dense medium.. which means n= c/v that speed should go down (eliminate A/C).

Now, f only varies with the source. v= fw (w = wavelength) so if v is to go down, w must also go down. So yea, I'm gonna go with B also.

EDIT: It's D, since the wavelength will be shorter in B..

 

[ThirdEye]

D

The angle is decreasing when refracted, so it's bending towards the normal which is correlated with slowing down. Bending away from the normal is correlated with speeding up.

It's slowing down from Medium A to Medium B. Since Medium A is faster, the wavelength in A is longer (v=fx)

 

[Jepstein30]

D

The angle is decreasing when refracted, so it's bending towards the normal which is correlated with slowing down. Bending away from the normal is correlated with speeding up.

It's slowing down from Medium A to Medium B. Since Medium A is faster, the wavelength in A is longer (v=fx)

doh.. read the answers wrong.. that makes total sense. Didn't catch the comparison in there..

too late and just did the 102 q. physics self assessment!!

 

[cloak25]

The answer is actually C...

 

[Dreamer29]

Because the light is bending towards the perpendicular in Medium B, we can assume that it travels slower in B than in A. We could equate A to air, and B to glass which is more dense. Frequency of light doesn't change when medium changes, and thus wavelength must be changing. Because speed decreases, wavelength must also decrease once in B. Thus, C is correct in that light was faster and had a larger wavelength in A than in B.

Lol, everyone has the correct reasoning; I just think we were all reading the answer choices wrong

 

[Jepstein30]

Oh.. thats poorly written. I was considering the answer as two separate statements:

Like: "It is faster" and "longer wavelengths in A than B"

Not how it wants it. "it is faster in A than B" and "longer wavelength in A than B"

thats sucky

 

[indianjatt]

Since medium A has an angle of 40 degrees and B has an incident of angle 30 degrees, we know light went from a medium with a lower index of refraction to one which is higher. So the speed must be higher in medium A. So A/C are possible choices. Since we know that the frequency only depends on the source, it will not change when we switch mediums. So V=lambda f. If the velocity is higher in medium A, the wavelength must also be higher (holding f constant).

 

[Temperature101]

Answer is C....