Water waves having parallel crests 4.9 cm apart pass through two openings 7.9 cm apart in a board. At a point 3.0 m beyond the board, at what angle(s) O (0° < < 90°) relative to the "straight-through" direction would
there be little or no wave action?

answer: good job it's all correct !

explanation:

i don't understand is there any other way you can rephrase it plz let me know in the comments and i will do it.

explanation:

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.