A monochromatic light is one that

Analysis

The question asks for the definition of "monochromatic light." In physics, particularly in optics, the term is derived from Greek roots: mono (one) and chroma (color).

Concept Explanation

Light is an electromagnetic wave characterized by its wavelength ($\lambda$) and frequency ($f$).

• Polychromatic light (like white light) is composed of many different wavelengths (colors) mixed together. When white light passes through a prism, it undergoes dispersion, splitting into its constituent colors (the visible spectrum).
• Monochromatic light consists of light of a single, specific wavelength (or frequency). Because it has only one wavelength, it cannot be split further into other colors.

Step-by-Step Solution

1. Evaluate Option A: Monochromatic light cannot undergo dispersion because dispersion is the separation of light into its constituent wavelengths. Since monochromatic light has only one wavelength, there is nothing to separate.
2. Evaluate Option B: Monochromatic light can definitely be refracted. Refraction occurs when light changes speed as it passes from one medium to another (e.g., from air to glass). This is the principle behind lenses and prisms.
3. Evaluate Option C: By definition, "mono" means one. Therefore, monochromatic light is light that consists of a single wavelength.
4. Evaluate Option D: This describes polychromatic light, not monochromatic light.

Conclusion

Based on the definition of monochromatic light, it is light characterized by a single wavelength.

Exam Tip: Whenever you see the prefix "mono-" in science (like monohybrid in Biology or monochromatic in Physics), always associate it with the number one. This will help you quickly eliminate options that suggest multiple components.