How to Work out the Critical Angle of a Substance
Make sure you know the Snell's Law., Find out the refractive index of the substance (or nx). , You can now do the substitution., The critical angle is therefore 41.8°.
Step-by-Step Guide
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Step 1: Make sure you know the Snell's Law.
The general form of Snell's Law is nxsinθx=nvacuumsinθvacuum, where n is the refractive index and θ is the angle of incidence or refraction. -
Step 2: Find out the refractive index of the substance (or nx).
, Let's say you are using glass with a refractive index of
1.50.
Therefore, the critical angle is the angle which, when it is the angle of incidence, produces an emergent ray of 90°. nglasssinθglass=nvacuumsinθvacuum
1.50sinθglass=1sin90° sinθglass=2/3 θglass=41.8° (correct to 3 significant figures) , -
Step 3: You can now do the substitution.
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Step 4: The critical angle is therefore 41.8°.
Detailed Guide
The general form of Snell's Law is nxsinθx=nvacuumsinθvacuum, where n is the refractive index and θ is the angle of incidence or refraction.
, Let's say you are using glass with a refractive index of
1.50.
Therefore, the critical angle is the angle which, when it is the angle of incidence, produces an emergent ray of 90°. nglasssinθglass=nvacuumsinθvacuum
1.50sinθglass=1sin90° sinθglass=2/3 θglass=41.8° (correct to 3 significant figures) ,
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Patricia Murray
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