Question

When sunlight passes through the window of your house, the dust particles scatter the light making the path of the light visible. This phenomenon is called as:

• A. Brownian motion
• B. Tyndall effect
• C. Raman effect
• D. Uniform motion

Hint:

The Tyndall effect is responsible for the visible beams of light that can be seen when light passes through dusty air.

Answer 1

The Correct Option is B

Step 1: Concept.
Dust particles are close in size to the wavelength of visible light, so they scatter sunlight strongly in many directions rather than letting it pass straight through.

Step 2: Match the term.
This scattering, which makes the path of a light beam visible, is different from Brownian motion, which is particle jitter, or the Raman effect, which is a wavelength shift, and is specifically called the Tyndall effect.

Step 3: Final Answer.
The phenomenon described is the Tyndall effect.

Answer 2

Thinking of other everyday moments where a light beam becomes visible helps confirm the answer.

1. Brownian motion: Watching fog swirl in car headlights is not about the fog particles jittering, it is about why the beam of light itself is visible, so this option is describing the wrong kind of observation.
2. Tyndall effect: Car headlights becoming a visible cone of light in fog, or a movie projector's beam showing up in a dusty theatre, are both classic everyday examples of this same effect, light scattering off small suspended particles so the path of the beam itself becomes visible. This matches the dust-in-sunlight scenario in the question exactly.
3. Raman effect: This effect needs sensitive instruments to detect a small shift in the colour of scattered light, and it is not something visible to the naked eye in everyday scenes like fog or dust in sunlight.
4. Uniform motion: Fog in headlights or dust in a sunbeam are not examples of anything moving at constant speed, so this option does not correspond to the scenario at all.

The same everyday phenomenon that lights up fog in headlights or a projector beam in a dusty room, light scattering by suspended particles, is what makes the sunbeam through the window visible.

So the correct answer is Tyndall effect.