Final answer:
Light bends when it enters a different medium due to B) change in speed.
Step-by-step explanation:
When light passes from one medium to another, such as from air to water or from air to glass, it changes speed and direction. This phenomenon is called refraction. The main reason light bends when entering a different medium is because the speed of light is different in different media.
Light waves have wave characteristics, including wavelength and frequency. When light travels from one medium to another, the speed of light changes, but the frequency remains the same. This means that the wavelength also changes to accommodate the change in speed. As a result, light rays bend or change direction when passing from one medium to another.
So, the correct answer to why light bends when it enters a different medium is B) Change in speed.