更多"Radio signals are waves that are us"的相关试题:
[单项选择]The British used radio waves because they______.
A. were more exact than sound waves
B. could not be detected
C. could penetrate fog and clouds
D. were easier to use than sound waves
[单项选择]If the radio waves had reached our planet one hundred years before, we would have______.
A. sent an immediate answer
B. sent an alarm against extraterrestrial attack
C. sent a short reply
D. sent no answer
[单项选择]The practical use of radio waves brought about______.
A. new machines for planes
B. a radio directing and ranging device
C. new radio sets for RAF bombers
D. a discovering device
[单项选择]The plane （） radio signals for help until site crashed.
A. gave out
B. went out
C. handed over
D. ran out of
[单项选择]Sound waves reflected from a hill can be used to calculate the______.
A. Speed of sound
B. time between a sound and ifs echo
C. height of the hill
D. distance of the hill
[单项选择]Sound waves reflected from a hill can be used to estimate______.
A. height of the hill
B. speed of sound
C. distance of the hill
D. intensity of sound
[单项选择]Such electronic devices（）are used in a radio set can also be found in a computer.
A. in which
B. that
C. which
D. as
[单项选择]Such electronic devices ______ are used in a radio set can also be found in a computer.
A. in which
B. that
C. which
D. as
[单项选择]
Because noises modulate radio frequency, radio stations use a band of frequencies to prevent interference with other stations.（）
A. govern
B. adapt
C. temper
D. renovate
[单项选择]What important discovery about seismic waves does the instructor mention
[单项选择]Mostocean waves are generatedby wind current that agitate the water's surface.
[单项选择]Seismic waves generated by an earthquake or large explosion can be recorded thousands of kilometer from their source.
[单项选择]Ocean waves can cut imposing cliffs along coastlines.（）
A. immobile
B. impermeable
C. impressive
D. imaginative
