Chapter 27, Problem 8Q

To determine

(a) To determine:

Does a beam of infrared photons always have less energy than a beam of ultraviolet photons?

Answer to Problem 8Q

Solution:

Yes, infrared photons have less energy than UV photons

Explanation of Solution

Formula used:

$\begin{array}{l}E=hf\\ \text{and }f=c/\lambda \\ \text{or }E=hc/\lambda \end{array}$

Here E is energy λ is wavelength and c is the speed of light.

UV photons always have more energy than infrared photons. The wavelength of UV is always below 365nm while the wavelength for infrared is always above 820nm, thus we can use the above formulas, the smaller the wavelength (λ)the higher the energy (E). Thus, we can conclude that infrared photons have less energy than UV photons.

To determine

(b) To determine:

Does a single infrared photon always have less energy than a single ultraviolet photon?

Answer to Problem 8Q

Solution:

Yes

Explanation of Solution

Yes, because no matter how intense the infrared light is, the energy of each individual photon remains the same.