Snell's Law

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SAT Subject Test in Physics › Snell's Law

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Light passes from a medium with some index of refraction $n_{1}$ at 25 degrees from perpendicular and exits into another medium with an index of refraction of 1.5 at an angle of 35 degrees. What is the value of $n_{1}$ ?

$n_{1}=\frac{1.5\sin(35)}{\sin(25)}$

$n_{1}=\frac{1.5\sin(25)}{\sin(35)}$

$n_{1}=\frac{\sin(25)}{1.5\sin(35)}$

$1.5\sin(35)$

$n_{1}=\frac{\sin(35)}{1.5\sin(25)}$

Explanation

Snell's law states:

$n_{1}\sin(\Theta _{1})=n_{2}\sin(\Theta _{2})$

If we substitute the values from the question we get:

$n_{1}\sin(25)=1.5\sin(35)$

Next rearrange to isolate $n_{1}$

$n_{1}=\frac{1.5\sin(35)}{\sin(25)}$

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