9. Which sound waves have a lower pitch?
Answer: B
Sound waves that are farther apart have a lower pitch.
When sound waves are farther apart, they have a lower frequency, which results in a lower pitch. This phenomenon is a key component of the Doppler Effect as described in the provided extract.
A) Sound waves that are closer together
Sound waves that are closer together have a higher frequency, which means they produce a higher pitch. This is the opposite of what the question is asking, as the closer proximity of sound waves leads to increased frequency rather than decreased.
B) Sound waves that are farther apart
Sound waves that are farther apart have a lower frequency, resulting in a lower pitch. This aligns perfectly with the explanation in the extract regarding how wave spacing affects the sound heard by the listener, making this the correct answer.
C) Sound waves that travel a long distance
The distance that sound waves travel does not directly determine their pitch. While sound can lose intensity over long distances, the pitch is more closely related to the frequency of the waves, which is not inherently affected by distance alone.
D) Sound waves that travel a short distance
Similar to option C, the distance traveled by sound waves does not dictate their pitch. Sound waves can be of any frequency regardless of the distance they travel, thus this option does not accurately answer the question.
Conclusion
The correct answer is definitively B, as it directly correlates with the established relationship between wave frequency and pitch. Other options either misinterpret the relationship or are irrelevant to the concept being tested regarding the Doppler Effect. Understanding that farther apart sound waves indicate a lower frequency is crucial for grasping this scientific phenomenon.