Ningbo underwater photography

A, as can be seen from the figure, the incident angles of the two beams of light are the same, but the refraction angle of B light is larger. According to the law of refraction, the frequency of light is small, and the wavelength is long in vacuum. According to n=cv=λ0fλf=λ0λ, λ0 is the wavelength of light in vacuum and λ is the wavelength of light in medium. Because the refractive index of light is small, n is the wavelength of light in the medium.

B, according to the critical angle formula sinC= 1n, it can be known that the refractive index of light A is small and its critical angle is large. If the position of incident point A is kept unchanged, the incident light rotates clockwise and the incident angle increases, then the critical angle of light B is reached first, so light B is totally reflected first and disappears from above the water surface, so B is wrong.

C, two beams of light travel at the same speed in vacuum, so C is wrong.

D and A light have small frequency and long wavelength. According to the fact that the interference fringe spacing of A light is proportional to the wavelength, we can know that the interference fringe spacing of A light is larger than that of B light, so D is correct.

Therefore, choose: d.