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PHY 104 Reflection and Refraction of Light Objective Question
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Question

A swimmer observes an object emitting 650 nm red light in air. If the swimmer observes the same object under water, where the wavelength of the light becomes 489 nm, why does the object still appear red to the swimmer?
Options
A The swimmer's eyes adapt to the change in wavelength underwater, interpreting 489 nm as red.
B The frequency of light remains constant when it passes from air to water, and color perception is determined by frequency, not wavelength.
Correct Answer
C The index of refraction of water causes a color shift, making blue light appear red.
D The human brain always interprets light from familiar objects as their true color, regardless of physical changes.
Correct Answer

Option B is the correct answer.

Detailed Explanation

Page 46 (Conceptual Example 32-10) addresses this: 'We said that color depends on wavelength. For example, for an object emitting 650 nm light in air, we see red. But this is true only in air. If we observe this same object when under water, it still looks red.' The underlying reason, which is a fundamental physics concept, is that the frequency of light does not change when it passes from one medium to another. Our perception of color is linked to the frequency of the light wave, not its wavelength, although wavelength is often used as a proxy for color in a single medium.

Hint

Consider what property of light remains constant when it changes medium: frequency or wavelength?

Question Info

Course: PHY 104
Topic: Reflection and Refraction of Light
Type: Objective
Difficulty: Not specified
Question 43 of 947
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