陳碧利

閉管音叉

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小明以頻率爲430赫的音叉,作共鳴空氣柱實驗,發現可以找到三個共鳴點,已知當時聲速爲344公尺/秒,

共鳴空 氣柱可視爲一端開口,一端封閉的空氣柱,則實驗所用的玻璃管長度i的範圍可能爲下列何者?

A. 80cm<L<85cm  B. 20cm<=L<=80cm  C.85cm<=L<100cm  D. 105cm<L<135cm

答案是D

我算出波長=344/430=0.8m=80cm

詳解說因為可找到三個共鳴點,所以5/4波長<=L<7/4波長->100cm<=L<140cm

Q1:我不知道5/4波長...到100cm<=L<140cm ,這段怎麼來的?閉口的公式是?

問題2:此題如果改開口樂器,要怎麼算呢?(可以改題目)開口的公式是?


可以詳細說明嗎? 謝謝

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