Q1. [1] medium thorough-understanding
When sunlight filters through a dense forest canopy containing mist, bright shafts of light become visible. Explain the optical phenomenon responsible for this observation and state what the visibility of these shafts tells us about the size of the particles present in the mist.
Generated by claude-sonnet-4-6 · 2026-06-26 01:09 · grounding rag
Model Answer
This is the Tyndall Effect — mist particles (tiny water droplets) scatter sunlight, making the beam's path visible. The visibility of white/bright shafts indicates the scattering particles are large enough (colloidal/larger size) to scatter all wavelengths.
Source: Chapter 10, Section 10.6.1 – Tyndall Effect
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Explanation
- Examiners expect the term Tyndall Effect to be named explicitly — that alone can fetch the mark.
- The second part (particle size) is the key inference: large particles scatter longer wavelengths too, so light appears white/bright rather than blue. Mention this briefly.
- Do not confuse with refraction or dispersion — the phenomenon here is scattering by colloidal particles.