QUESTION 3 The explanation for refraction must involve a change in Warm air you
- A. speed.
- B. frequency.
- C. wavelength.
- D. all of these.
Cool air of sound.
The Correct Answer and Explanation is:
Correct Answer: A. speed
Explanation
Refraction refers to the bending of a wave as it passes from one medium into another where its speed changes. In the case of sound waves, refraction occurs when the sound moves through air layers of different temperatures, such as from warm air to cool air or vice versa.
When sound travels from warm air into cool air, its speed decreases. This is because the speed of sound is directly related to the temperature of the medium—the warmer the air, the faster the molecules move, allowing sound waves to propagate more quickly. In cooler air, molecules move more slowly, reducing the sound speed.
This change in speed causes the direction of the sound wave to bend, which is what we call refraction. The bending occurs toward the region of lower speed—in this case, toward the cooler air. This phenomenon is why sound can sometimes be heard more clearly at night when the air near the ground is cooler than the air above, causing the sound to bend back toward the earth instead of dispersing into the sky.
Now, let’s address the other options:
- B. Frequency: The frequency of a wave is determined by the source and does not change when a wave passes from one medium to another. Therefore, frequency remains constant during refraction.
- C. Wavelength: Wavelength does change, but this is a result of the change in speed, not the cause of refraction. Since the speed changes and frequency stays the same, the wavelength must adjust accordingly (v = fλ).
- D. All of these: This is incorrect because only speed and wavelength change, while frequency remains unchanged. Therefore, “all of these” is not the right choice.
Conclusion:
Refraction of sound due to temperature differences in air is primarily caused by a change in speed, making Option A: speed the correct answer.
