Final answer:
Red light can support photosynthesis, but typically less efficiently than when a plant is exposed to a full spectrum of light. The wavelength of light decreases as it moves from a vacuum into water. The energy of light necessary for the photoelectric effect increases with its frequency.
Step-by-step explanation:
When it comes to photosynthesis and light wavelength, different pigments within plants absorb light at different wavelengths. For instance, chlorophyll, the primary pigment for photosynthesis, absorbs light most efficiently in the red and blue parts of the spectrum and less efficiently in the green. Therefore, if a plant were exposed to only red light, photosynthesis would still be possible. According to the options provided, the most accurate would likely be that the rate of photosynthesis decreases slightly under red light compared to a full spectrum, because while red light is absorbed well, it is not the only wavelength that chlorophyll absorbs, and other wavelengths can contribute to even higher rates of photosynthesis.
In the context of light passing through different media, when light slows down as it transitions from one medium to another, such as from air to water, its wavelength shortens, but its frequency remains constant since frequency is a property of the source and unaffected by medium changes. For monochromatic light moving from a vacuum into water, the wavelength decreases (option d).
When discussing the photoelectric effect, the quantum explanation of the phenomenon indicates that the energy of light increases with its frequency (option c), which is why light must have a frequency (or a wavelength shorter than a specific threshold) to cause the emission of electrons from a metal surface.