A Level Physics Practice Exam

In the transition of monochromatic light from air to water, what characteristics change?

1. Velocity and frequency

2. Wavelength and frequency

3. Velocity and wavelength

4. Frequency only

The correct answer is: Velocity and wavelength

In the transition of monochromatic light from air to water, the key characteristics that change are the velocity and wavelength of the light. When light enters a denser medium like water from a less dense medium such as air, it slows down due to the increased optical density of water. This change in velocity is accompanied by a change in wavelength; specifically, the wavelength decreases because the frequency of the light remains constant. Frequency is determined by the source of the light and does not change when the light transitions between different media. So, while the velocity and wavelength change, the frequency stays the same, making the correct answer focused specifically on the aspects that do vary during the transition. This distinction is crucial in understanding wave behavior as it crosses boundaries between different materials.