Final answer:
Snell’s law approximations include treating air's index of refraction as 1 and using the small-angle approximation where sin θ ≈ θ. These are generally acceptable and result in minimal errors under standard conditions.
Step-by-step explanation:
The question pertains to the assumptions or approximations made in the application of Snell’s law. Snell's law, which is n₁ sin θ1 = n₂ sin θ2, indicates the relationship between the angles of incidence (θ1) and refraction (θ2), and the indices of refraction (n₁ and n₂) of two media. The primary approximation in applying Snell's law is the assumption that the index of refraction for air is 1. This is a reasonable approximation since the actual value up to four significant figures is very close to 1.000. Another assumption, particularly when using the small-angle approximation, is that sin θ ≈ θ, which is commonly valid for small angles measured in radians.
In cases where precision is crucial, and the angle of incidence is not small, or if the true index of refraction of air differs significantly from unity due to conditions like extreme atmospheric pressure or humidity, these approximations may introduce errors. However, under standard conditions and for educational purposes, these approximations are generally deemed to be reasonable and cause negligible errors in calculations.