Final answer:
Using Snell's Law, the angle of refraction for a narrow beam of sodium yellow light with a wavelength of 589 nm going from air to water with an angle of incidence of 40 degrees is approximately 28.7 degrees.
Step-by-step explanation:
To find the angle of refraction when a narrow beam of sodium yellow light, with a wavelength of 589 nm in vacuum, is incident from air onto a smooth water surface, we use Snell's Law. Snell's Law states that n1 * sin(i) = n2 * sin(r), where n1 is the refractive index of the first medium (air in this case, with an index of 1.0), i is the angle of incidence, n2 is the refractive index of the second medium (water, with an index of 1.33), and r is the angle of refraction. Given an angle of incidence of 40 degrees, we can solve for r.
n1 * sin(i) = n2 * sin(r)
1.0 * sin(40 degrees) = 1.33 * sin(r)
sin(r) = sin(40 degrees) / 1.33
sin(r) ≈ 0.643 ≈ 0.484
r ≈ sin-1(0.484)
r ≈ 28.7 degrees