Q. The wave of wavelength $5900\ \mathring{\mathrm{A}}$ 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
A) $4.068 \times 10^{8}$
B) $4.068 \times 10^{7}$
C) $4.068 \times 10^{6}$
D) $4.068 \times 10^{5}$
Explanation
(c) Number of oscillator in coherence length
$= \frac{l}{\lambda} = \frac{0.024}{5900 \times 10^{- 10}}$
$= 4.068 \times 10^{6}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.