Given the above information, and given that solids generally have greater optical densities than liquids, and that liquids generally have greater optical densities than gases, which of the following statements is true?the number of wavelengths per unit time will not change as a light wave moves from a solid into a liquid.

Optical density is defined as the ratio of speed of light in air with speed of light in any given medium

so it is given as

now we have as per above equation

speed of light = frequency * wavelength

so we can write

and also

so the frequency of light will not change as we move from one medium to another medium.

As per above equation we can also write

explanation: magnetic pole, region at each end of a magnet where the external magnetic field is strongest. the south-seeking pole, or any pole similar to it, is called a south magnetic pole. unlike poles of different magnets attract each other; like poles repel each other.

i think the answer is a, hope this : )