Light travels from air (n1 = 1.0) into glass (n2 = 1.5) with an angle of incidence of 30 degrees. What is the angle of refraction? (Use sin 30 = 0.5, and arcsin(0.333) = 19.5 degrees)
Show the answer and explanation
Correct answer
A. 19.5 degrees
Principle or equation
Snell's law: n1 * sin(theta1) = n2 * sin(theta2).
Why this answer is correct
sin(theta2) = (n1 * sin(theta1)) / n2 = (1.0 * 0.5) / 1.5 = 0.333. Therefore, theta2 = arcsin(0.333) = 19.5 degrees.
Example
If light goes from water (n=1.33) to air (n=1) at 45 degrees, sin(theta2) = 1.33 * sin(45) = 0.94, so theta2 ≈ 70 degrees.
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