matt2minger
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#1
Report Thread starter 11 years ago
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Hi,

When you get an equation like the following:

SinC = 1 / 1n2

What does the 1n2 bit mean?
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spook2575
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im taking a guess here, but 1n2 could mean ln2, which is around 0.69.
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matt2minger
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no,

its something to do with the refractive index of one object (1), and the refractive index of another substance (2).

But im not sure how to use the equatrion
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MC REN
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refractive index going from material with index n1 to that with index n2

so it is just alternative notation for n2/n1 in this case (i think, could be n1/n2 I guess cause I don't know why they have bothered putting 1 / 1n2 instead of 2n1 or whatever and it has been a while since i've seen this notation - should be clear from snell's law/what the question says which way round to do it though)
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Zwitter Ion
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the equation is to calculate the critical angle of a wave moving from 1 medium to another that is medium 1 (n1) to medium 2 (n2)
such as a wave travelling from water (n1) to glass(n2)...and then you just sin-1 the answer to get the critical angle hope that makes sense
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lucic17
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1 is the medium the wave is coming from
2 is the medium wave is entering
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tgnhje
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I thought 1 is the medium the wave is entering and two is the medium the wave is coming from, in this case.

If a wave is going from medium 1 to medium 2, then

1n2 = sin C/1

so 2n1 = 1/sin C

sin C * 2n1 = 1

sin C = 1 / 2n1

so 2n1, where 2 is the material it's entering and 1 is the matieral it's coming from?

I'm very confused about all this.
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lucic17
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1n2 = 1 / sin C

relative refractive index, 1n2 = n2 / n1 , which u use when you're not dealing with a vacuum/air.

n2 and n1 are the absolute refractive indices of the respective media.
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tgnhje
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(Original post by lucic17)
1n2 = 1 / sin C

relative refractive index, 1n2 = n2 / n1 , which u use when you're not dealing with a vacuum/air.

n2 and n1 are the absolute refractive indices of the respective media.
Is medium 1 the medium the ray is leaving or entering?
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pisces_abhi
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It's \sin\theta_c=\frac{n_2}{n_1}

n_2 is the refractive index of the medium the ray is leaving or currently traveling in

n_1 is the refractive index of the medium the ray is going to enter
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