Light and Optics — Visible Spectrum How many distinct colours are traditionally recognized in the sunlight (visible) spectrum?

Introduction / Context:
The visible spectrum is the portion of electromagnetic radiation detectable by the human eye. When white sunlight is dispersed by a prism or water droplets, it separates into constituent wavelengths perceived as colours. Educational convention often enumerates these as seven distinct colours, remembered by the mnemonic VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red).

Given Data / Assumptions:

• Traditional school-level classification is used.
• The question seeks the standard count, not a discussion of continuous spectra.
• Human perception groups continuous wavelengths into categories.

Concept / Approach:
Although the spectrum is continuous, cultural and pedagogical tradition recognizes seven colours for simplicity. This aligns with common curricula and basic optics problems. The count arises from historical choices (e.g., Newton’s division aligning with musical notes), not from discrete physical boundaries.

Step-by-Step Solution:

Verification / Alternative check:
Observing a rainbow or a prism experiment reproduces the ordered sequence; textbooks list seven named bands.

Why Other Options Are Wrong:

• Three, Four, Five: Undercount the commonly taught categories.

Common Pitfalls:
Overthinking the continuous nature of spectra. Exams typically expect the conventional “seven colours” answer unless otherwise specified.

Final Answer:
Seven