Question

The danger signals installed at the top of tall buildings are red in color. These can be easily seen from a distance because among all other colors, red light

• A. is scattered the most by smoke or fog.
• B. is scattered the least by smoke or fog.
• C. is absorbed the most by smoke or fog.
• D. moves fastest in air.

Hint:

Scattering is inversely related to wavelength:
\[ \text{Wavelength } (\lambda) \uparrow \implies \text{Scattering } \downarrow \]
Red has the largest \(\lambda\) among visible colors, so it scatters the least and travels the farthest.

Answer 1

The Correct Option is B

Step 1: Recall how scattering depends on wavelength.
The amount a light ray gets scattered by tiny particles like smoke or fog droplets falls off very sharply as the wavelength of the light increases.
Step 2: Compare red with the rest of the visible spectrum.
Among all the colours we can see, red light has the longest wavelength, so out of every colour it is the one that gets scattered the least by smoke, dust or fog.
Step 3: Think about what that means for visibility.
Because it barely gets scattered away, red light keeps travelling in a fairly straight, undiminished beam even through hazy or foggy air, while blue and violet light get thrown off in all directions and fade out quickly.
Step 4: Apply this to danger signals.
That is exactly why tall buildings use red warning lights, they remain clearly visible from far away even in poor visibility.
\[ \boxed{\text{is scattered the least by smoke or fog}} \]