Question

A certain type of laser emits light that has a frequency of 4.2 × 1014 Hz. The light, however, occurs as a series of short pulses, each lasting for a time of 3.2 × 10-11 s. (a) What is the wavelength of this light? (b) How many wavelengths are there in one pulse?

Answer 1

Explanation:

It is given that,

Frequency of the laser light, $f=4.2\times 10^{14}\ Hz$

Time, $t=3.2\times 10^{-11}\ s$

(a) Let $\lambda$ is the wavelength of this light. It can be calculated as :

$\lambda=\dfrac{c}{f}$

$\lambda=\dfrac{3\times 10^8}{4.2\times 10^{14}}$

$\lambda=7.14\times 10^{-7}\ m$

or

$\lambda=714\ nm$

(b) Let n is the number of the wavelengths in one pulse. It can be calculated as :

$n=f\times t$

$n=4.2\times 10^{14}\times 3.2\times 10^{-11}$

n = 13440

Hence, this is the required solution.