Final answer:
Performing Young's double-slit experiment in water results in smaller angles in the interference pattern due to the decreased wavelength of light, although the color of the light remains unchanged.
Step-by-step explanation:
When performing Young's double-slit experiment, the observed interference pattern is a result of the wavelength of the light and the medium through which it travels. In water, the wavelength of light decreases because the speed of light is slower in water compared to air. This change in wavelength affects the diffraction of light as it passes through the slits, which in turn alters the interference pattern. The angles to the same parts of the interference pattern get smaller in water because the reduced wavelength means the waves spread out less after passing through the slits.
The color of the light, which is determined by its frequency, remains unchanged because the frequency of light does not change when transitioning between mediums. The color perceived by an observer also stays the same since the frequency, which determines color, does not change.
Therefore, the correct answer to the student's question is: d. Angles get smaller in water; the color of the light remains the same.