Two light sources are said to be coherent if they ( )
A: are of the same frequency.
B: are of the same frequency and amplitude.
C: are of the same amplitude, and maintain a constant phase difference.
D: are of the same frequency, and maintain a constant phase difference.
A: are of the same frequency.
B: are of the same frequency and amplitude.
C: are of the same amplitude, and maintain a constant phase difference.
D: are of the same frequency, and maintain a constant phase difference.
举一反三
- The difference between a histogram and a frequency polygon is:
- Phase lag compensation can reduce the cut-off frequency of the system after compensation by means of_____ in the intermediate and high-frequency band of the original system, so as to obtain sufficient phase margin with the help of the phase at this frequency of the original system. A: magnitude attenuation B: phase lag C: magnitude increase D: magnitude unchanged
- The index of coincidence: A: can tell you the likelihood that a key is the same length as the ciphertext B: can tell you the likelihood that some ciphertext has the same frequency counts as English C: can distinguish between mono and polyalphabetic substitution ciphers D: a and b only.
- There is no difference between the cultures that are classifying into the same categories as either high or low-contact.
- The difference between a histogram and a frequency polygon is: A: the frequency polygon is reported as a percent, a histogram does not report percents. B: the histogram shows frequencies while a frequency polygon shows cumulative frequencies. C: the bars in a histogram and a frequency polygon cannot be adjacent. D: open-ended classes can be accommodated with a frequency polygon.