Answer:
It moves along straight lines in air and changes direction when it enters water.
Step-by-step explanation:
When light travels from one medium to another, it undergoes a phenomenon called refraction: the ray of light changes speed and also direction, but it continues to move in a straight line.
There is a relationship between the direction of the incident ray and the direction of the refracted ray: (Snell's Law)
where
n1 is the index of refraction of the first medium
is the angle that the incident ray forms with the normal to the surface
n2 is the index of refraction of the second medium
is the angle that the refracted ray forms with the normal to the surface