An open pipe of air supports standing waves at frequencies of 300 Hz and 400 Hz. There are no other frequencies between these two. What is the frequency of the second harmonic of this tube?
A: 100 Hz
B: 200 Hz
C: 400 Hz
D: 600 Hz
A: 100 Hz
B: 200 Hz
C: 400 Hz
D: 600 Hz
举一反三
- 信号[img=311x80]18031101f62af38.png[/img]的奈奎斯特频率为( )。(注:符号 ⃰ 表示卷积) A: 100 Hz B: 200 Hz C: 400 Hz D: 500 Hz
- 工频的频率是( ) A: 50Hz B: 60 Hz C: 100 Hz D: 200 Hz
- 噪声频率在Hz的中频噪声不会对人体造成伤害() A: 100~200 B: 200~400 C: 400~600 D: 300~800
- 国内交流电工作频率() A: 30Hz B: 50 Hz C: 60 Hz D: 100 Hz
- 电容式接近开关:抗干扰性能好,开关频率高,大于()HZ A: 100 B: 200 C: 300 D: 400