The wave of wavelength 5900 Å emitted by any atom or molecule must have some finite total length which is known as the coherence length. For sodium light, this length is 2.4 cm. The number of oscillations in this length will be

4.068 × 10⁶

Number of oscillator in coherence length

$\frac{l}{λ}=\frac{0.024}{5900×10^{-10}}$

$=4.068 × 10^6$