Answer:
When unpolarized light is reflected off a non-metallic surface at a specific angle of incidence, the reflected light becomes polarized. This angle of incidence is known as Brewster's angle and can be calculated using the formula:
tan θp = n
where θp is Brewster's angle and n is the refractive index of the medium the light is passing into.
In this case, the light is passing from air (which has a refractive index of approximately 1) into water with a refractive index of 1.3. Therefore, we can plug in the values into the formula and solve for θp:
tan θp = 1.3
θp = tan^-1(1.3)
Using a calculator, we get θp = approximately 53.1 degrees.
Therefore, light reflected from water will be completely polarized at an angle of incidence of approximately 53.1 degrees.