hce_nthu
113年
資訊科學
第 20 題
Beat is an interference phenomenon when two waves of slightly different frequencies are superposed. How does the beat frequency change when both sound sources (of slightly different frequencies) move relative to the stationary listener?
- A It does not change if both sound sources approach the listener at the same speed.
- B It increases if both sound sources approach the listener at the same speed.
- C It decreases if one sound source approaches and the other moves away from the listener at the same speed.
- D It increases if one sound source approaches and the other moves away from the listener at the same speed.
- E None of the above is false.
思路引導 VIP
試著思考一下：如果我們有兩個數字（例如 10 和 12），當我們把這兩個數字同時乘以一個「大於 1 的倍數」時，這兩個新數字之間的『差距』，會比原本的差距（2）變得更大、更小，還是保持不變呢？
🤖
AI 詳解
AI 專屬家教
恭喜你精確地判斷出正確答案！這題的核心在於將**多普勒效應（Doppler Effect）與拍頻（Beat Frequency）**的概念結合應用，你能迅速理清兩者間的數學關係，表現得非常出色。
多普勒效應與頻率差的放大
拍頻的本質是兩波源頻率之差的絕對值，即 $f_{beat} = |f_1 - f_2|$。當兩個聲源以相同速度 $v_s$ 向靜止觀察者靠近時，根據多普勒效應公式，觀察者接收到的頻率會變為：
▼ 還有更多解析內容