Question

Name and explain the phenomenon of light due to which the path of a beam of light becomes visible when it enters a smoke filled room through a small hole. Also state the dependence of colour of the light we receive on the size of the particle of the medium through which the beam of light passes.

Answer 1

Phenomenon: Tyndall Effect
The path of a beam of light becomes visible in a smoke-filled room due to the Tyndall Effect. This phenomenon occurs when light is scattered by the particles present in the medium (such as smoke, dust, or colloidal particles). The scattering makes the path of the
light visible.
Explanation: The smoke particles in the air are large enough to scatter the light in different directions, which makes the light beam visible. This scattering depends on the size of the particles relative to the wavelength of light.
Dependence of colour on particle size:
• Smaller particles scatter shorter wavelengths of light (like blue and violet) more effectively. This is why the sky appears blue.
• Larger particles scatter all wavelengths of light approximately equally, which can result in the scattered light appearing white.