Question

What is the distance between a crest and a trough in a wave?
A. $\lambda $
B. $\lambda /2$
C. $\lambda /4$
D. $2\lambda $

Answer 1

Hint: Waves originate from a disturbance and the energy of such disturbances propagate in the form of waves. The main characteristic of a wave is its repetitive motion. Waves have moving alternate crests and troughs. A crest of the wave refers to the highest part of that wave and the trough refers to the lowest part of the wave. A crest is a point of the wave at which displacement of the medium will be maximum and on the other hand, at trough there is a least displacement of medium.

Complete step by step answer:
If we consider a wave cycle, a wave originates from its starting point and goes up to form a crest then goes down to form a trough and then return back to its starting point. Any type of wave, whether it is sound wave, electromagnetic wave or sea wave, the distance between a crest and trough is known as wavelength of that wave. The given below figure shows the crest, trough and wavelength of a wave.

For mathematical purposes, a wavelength is denoted by the Greek letter lambda or $\lambda $. The units used for measuring wavelength of the waves are meter, centimeter or nanometer and it depends upon the type of wave. The distance between a crest and a trough in a wave is wavelength and is denoted by $\lambda $.

Hence, the correct option is option A.

Note: The wavelength is related to the horizontal distance between a crest and a trough. Similarly, wave height is the vertical distance between the crest and trough of a wave. The amplitude of a wave and wave height are not the same. Amplitude of the wave is half the wave height. The amplitude is considered as the measure of intensity of the wave.