What are the two laws of refractive index?
GeneralClass 12AllAnswered 27 Mar 2026
Answer
The two fundamental laws of refraction (also called Snell's laws) are:
- First Law: The incident ray, the refracted ray, and the normal to the interface at the point of incidence all lie in the same plane.
- Second Law: For a given pair of media and for light of a given wavelength, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This constant is the refractive index: sin i/sin r = n₂₁ (constant)
These laws govern all refraction phenomena and are essential for understanding optical systems.
Why is sin 270° = -1?
Sin 270° equals -1 because at 270° on the unit circle, the point is at coordinates (0, -1). The sine function represents the y-coordinate, which is -1 at this angle. This is three-quarters of the way around a circle from 0°, pointing straight down along the negative y-axis.
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