Final answer:
The wavelength of light decreases to 0.750 times its original value when it passes from air to water, with the correct answer being option a) 0.750.
Step-by-step explanation:
When light passes from air to water, the factor by which its wavelength decreases is 0.750. This can be explained by considering the refractive index of water, which is typically around 1.33. The speed of light in a medium is given by the equation speed = (speed of light in vacuum) / (refractive index).
Since the frequency of the light does not change, the wavelength must decrease in the water to ensure the wave equation (speed = frequency x wavelength) holds true. Using the refractive index of water, it can be shown that the wavelength of light decreases to approximately 75% of its original value in air. Therefore, the correct option for the question is a) 0.750.
It's important to note that while the wavelength of light decreases, the frequency remains the same when transitioning from one medium to another. This is because the change in medium affects the speed of light and thus the wavelength, but not the oscillation of the electromagnetic wave that is the frequency.