Science (086) — CBSE Class 10 board question

The path of a beam of light passing through a colloidal solution is visible due to the Tyndall effect. The colloidal particles are relatively larger in size than the particles of a true solution. When light strikes these colloidal particles, they scatter light in all directions. This scattered light reaches our eyes, making the path of the beam visible. This phenomenon is called the Tyndall effect.

Source: Chapter 10, Section 10.6 – Scattering of Light / 10.6.1 Tyndall Effect

• The key term examiners look for is Tyndall effect — always name it.
• The core reason is scattering of light by colloidal particles (which are larger than particles in a true solution).
• Contrast with a true solution (path not visible) to strengthen the answer — it shows conceptual clarity.
• This is typically a 2–3 mark question; the answer above covers all required points concisely.