Question

Chromatic aberration arises in thick lenses due to:

• A. scattering of light
• B. refraction of light
• C. interference of light
• D. reflection of light
• E. dispersion of light

Hint:

"Chroma" means color; chromatic aberration is always related to the dispersion of colors.

Answer 1

Answer: (E)

Step 1: Understanding the Concept:
This is a conceptual question about optical aberrations in lenses. Chromatic aberration is a specific type of image defect.
Step 2: Detailed Explanation:
Let's define the terms: - Chromatic Aberration: This is a failure of a lens to focus all colors of light to the same point. It occurs because lenses have a different refractive index for different wavelengths (colors) of light. When white light passes through a lens, the different colors are bent by slightly different amounts. This causes the light to spread out, resulting in colored fringes around images. - Dispersion of Light: This is the phenomenon in which the refractive index of a material depends on the wavelength of light. Because of dispersion, a prism splits white light into its constituent colors (a spectrum). - Refraction of Light: This is the bending of light as it passes from one medium to another. While refraction is necessary for a lens to work, it is the variation of refraction with color that causes the problem. - Scattering, Interference, Reflection: These are other light phenomena but are not the direct cause of chromatic aberration in lenses. The root cause of chromatic aberration is that the material of the lens (e.g., glass) causes dispersion. Because of dispersion, the focal length of the lens is slightly different for each color. For example, in a simple convex lens, the focal length for blue light is shorter than the focal length for red light. This causes the different colors to focus at different points, creating the aberration.
Step 3: Final Answer:
Chromatic aberration arises due to the dispersion of light by the lens material.