Answer:
E) its speed and wavelength decrease, but its frequency stays the same
Explanation:
First of all, the frequency of a light wave does not depend on the medium, while wavelength and speed do. Therefore, the frequency remains costant.
In particular, the speed of light in a medium is given by:
where c is the speed of light in a vacuum and n is the index of refraction. From the formula, we see that v and n are inversely proportional: so, when the light moves into a material with higher index of refraction, its speed decreases.
Moreover, speed is related to wavelength by
where is the wavelength and f is the frequency. Since the two quantities are directly proportional, this means that since the speed decreases, the wavelength decreases as well.
So, the correct choice is
E) its speed and wavelength decrease, but its frequency stays the same
