Chapter 27, Problem 1STP

To determine

To choose: The correct option.

Answer to Problem 1STP

Option A: Energy of each photon is $3.135\times {10}^{-19}\text{J}$ .

Explanation of Solution

Given data:

Wavelength of a helium-neon laser is $\text{632}\text{.8 nm}$ .

Formula Used:

  $E=\frac{hc}{\lambda }$

Here, h is the Planck’s constant, c is the speed of light and $\lambda$ is the wavelength.

Calculation:

The energy of each photon is calculated as:

  $\begin{array}{l}E=\frac{hc}{\lambda }\\ =\frac{1240\text{}\text{ eV-nm}}{632.8\text{ nm}}[hc=1240\text{ eV-nm]}\\ =1.9595\text{ eV}\end{array}$

The energy in Joules is calculated as follows:

  $\begin{array}{l}E=\left(1.9595\text{ eV}\right)\left(\frac{1.60\times {10}^{-19}\text{ J}}{1\text{ eV}}\right)\\ =3.135\times {10}^{-19}\text{J}\end{array}$

Conclusion:

Energy of each photon is $3.135\times {10}^{-19}\text{J}$ . Thus, option A is correct.