Final answer:
Using Snell's Law, we determine the angle of incidence of a light ray crossing from water to glass, with given indices of refraction, to be approximately 41.8 degrees.
Step-by-step explanation:
When a light ray crosses from water into glass and emerges at an angle of 30° to the normal, we can determine its angle of incidence using Snell's Law. Snell's Law states that n1 · sin(θ1) = n2 · sin(θ2), where n1 and n2 are the indices of refraction for the first and second medium, and θ1 and θ2 are the angles of incidence and refraction, respectively.
Given the indices of refraction for water (1.333) and glass (1.50), and the angle of refraction in glass (θ2 = 30°), we can solve for the angle of incidence in water (θ1). The equation to find the angle of incidence is 1.333 · sin(θ1) = 1.50 · sin(30°). Solving this equation, we get: θ1 = sin-1((1.50 · sin(30°)) / 1.333).
By calculating the above expression we find that θ1 ≈ 41.8°, which means the angle of incidence in water is approximately 41.8°.