Q. The waves of wavelength $5900\ \mathring{\mathrm{A}}$ emitted by any atom or molecule must have some finite total length which is known as 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) $4.068 \times 10^{4}$
C) $4.068 \times 10^{6}$
D) $4.068 \times 10^{5}$
Explanation
(b) Newton’s of oscillations in coherence length
$\frac{l}{\lambda} = \frac{0.024}{5900 \times 10^{- 10}}$
$= 40677.9 = 4.068 \times 10^{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.