A beam of light makes an angle of 60 degrees with the surface of a window as it passes through. If the index of refraction for the glass is 1.50, determine the angle of refraction.

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t-nez eNotes educator| Certified Educator

Snell's Law describes how light bends when it passes from one medium into another medium with a different index of refraction, because light had a different speed in each substance:

n1 sin θ1= n2 sin θ2

Where n2 and n2 represent indices of refraction and θ1 and θ2 represent incident and refracted angles that correspond to the two substances. In this case light is moving from air, which has an index of refraction of 1.00, into glass which has an index of refraction of 1.50 at an incident angle of 60 degrees, so the equation is:

(1.00)(sin 60) = (1.50) sin θ2, 

so θ2 = sin^-1 (sin 60/1.50) 

= sin^-1(0.577) = 35.2 degrees

So the light ray that strikes the glass at an angle of 60 degrees to the normal (normal is perpendicular to the glass) will be refracted or bent to an angle of 35.2 degrees to the normal when it slows upon entering glass, a more optically dense substance.