Chapter 28, Problem 26A

To determine

To explain: The reason for painting the interiors of optical instruments black.

Explanation of Solution

Introduction:

In imaging systems, the absorption of light is an important consideration to improve the efficiency of the optical instruments. So, it is necessary to decrease the reflection in optical instruments.

Explanation: 

To improve the efficiency of optical instruments, it is necessary to decrease the reflection of light, for example, to improve the performance of telescopes and microscopes. To decrease the reflection, coatings are helpful. They exhibit strong absorption in the light and suppress stray light in optical instruments. High absorption results in high emissivity. Black coating or paint is usually more effective in the absorption of light at all wavelengths and also at angles that are close to the surface of the optics. Thus, black paint is the anti-reflect agent and it absorbs the light to improve the efficiency of optical instruments.