Question

Why does the wavelength of light decrease when it passes from vacuum into a medium? State which attributes change and which stay the same and, thus, require the wavelength to decrease.

a) The frequency decreases, and speed stays the same, requiring the wavelength to decrease.

b) The speed decreases, and frequency stays the same, requiring the wavelength to decrease.

c) The speed decreases, and wavelength stays the same, requiring the frequency to decrease.

d) The frequency increases, and speed stays the same, requiring the wavelength to decrease.

Answer 1

The wavelength of light decreases when it passes from a vacuum into a medium because the speed of light slows down while the frequency remains constant, necessitating a decrease in wavelength.

Step-by-step explanation:

When light travels from a vacuum into a medium such as water, the wavelength of light decreases and the speed of light decreases.

This happens because the frequency of the light wave does not change when it passes between media — it is a property that is determined by the source of light and remains constant. The speed of light in a medium is given by v = c/n, where c is the speed of light in a vacuum and n is the index of refraction of the medium.

Since the speed of light is slower in a medium (v < c), and the frequency (f) remains the same, the wavelength (λ) has to decrease according to the relationship v = fλ. Therefore, the correct statement for this concept is b) The speed decreases, and frequency stays the same, requiring the wavelength to decrease.