Question

The S.I. unit of wavelength is _______________
$
  A.{\text{ cm}} \\
  {\text{B}}{\text{. dm}} \\
  C.{\text{ m}} \\
  D.{\text{ km}} \\
 $

Answer 1

Hint: Here we will proceed by writing the formula of wavelength because from that we can easily calculate the S.I. unit of wavelength.

Complete Step-by-Step solution:
Wavelength is defined as the distance between the maximum displacement of amplitude from equilibrium. It is the space generated in a periodic wave-the distance over which the wave’s shape is repeated.

Wavelength $ = \dfrac{{speed{\text{ of light}}}}{{frequency}}$
In terms of symbols,
$\lambda = \dfrac{v}{f}$
$\lambda = $ refers to the wavelength, the distance between the crests in meters(m)
$v = $ refers to the velocity of speed of waves are moving in a direction in meter per seconds $\left( {\dfrac{m}{s}} \right)$
$f = $ refers to the frequency, the wave crests that go through a point in certain time cycles per second or hertz $\left( {\dfrac{{cycles}}{{\sec }}} \right)$ or Hz.
Wavelength is the distance between two successive crests of a wave. It is always measured in the direction of the propagation of waves.
As wavelength is basically the distance, so the S.I. unit of wavelength is meters(m)
Therefore, the correct option is C.

Note: Whenever we come up with this type of problem where we are asked to find out the unit of any quantity. Then we first write the formula after that by expanding the formula we will get the required standard unit asked for that quantity. (Here S.I. unit of wavelength).