更多"频率（frequency）"的相关试题:
[填空题]Traffic accidents occur with alarming frequency, ______ (造成国家财产和生命的巨大损失).
[填空题]Spread-spectrum frequency can transmit the same frequency at the same time for more than one device.
[单项选择]频率：赫兹
A. 压力：帕斯卡
B. 力：牛顿
C. 质量：分
D. 线密度：盎司
[单项选择]Microwave communication uses high-frequency (71) waves that travel in straightlines throughthe air. Because the waves cannot (72) with the curvature of the earth, they can be (73) only over short distance. Thus, microwave is a good (74) for sendingdata between buildings ina city or on a large college campus. For longer distances, the wavesmust be relayed by means of"dishes" or (75) . These can be installed on towers, highbuildings, and mountain tops.
A. optical
B. radio
C. electrical
D. magnetic
[单项选择]哪一频率不在超声的频率范围（）
A. 10000Hz
B. 1000，000Hz
C. 1MHz
D. 0.1Hz
E. 20MHz
[单项选择]较高频率电流的幅度或频率随另一种较低频率电流的幅度变化而变化称为（）
A. 载波
B. 调制
C. 差频
D. 差拍
E. 调幅度
[判断题]带宽指信道所能送的信号的频率宽度，就是可传送信号的最高频率与最低频率之差。
[单项选择]
Microwave communication uses （） -frequency radio waves that travel in straightline sthrough the air. Because the waves cannot （） with the curvature of the earth, they can be （） only over short distance. Thus, microwave is a good （） for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or （） . These can be installed on towers, highbuildings, and mountain tops.
Because the waves cannot （） with the curvature of the earth.
A. reflex
B. distort
C. bend
D. absorb
