Question

At sunrise or at sunset the sun appears to be reddish while at midday it looks white. This is because

A. Scattering due to dust particles and air molecules causes this phenomenon
B. The sun is cooler at sun rise or at sunset
C. Refraction causes this phenomenon
D. Diffraction sends red rays to the earth at these times

Answer 1

Hint: Scattering of light is a phenomenon in which the light rays get deviated from its path on striking small objects like dust particles, gas molecules or air molecules having dimensions less compared to the wavelength of the light. White light is composed of 7 colours (VIBGYOR).

Formula used:
$$I\propto {\displaystyle \frac{1}{{\lambda }^4}}$$

Complete answer:
Rayleigh scattering is the scattering of light by small particles with respect to the wavelength of the incident light.
The intensity of light is inversely proportional to the fourth power of the wavelength.

$$I\propto {\displaystyle \frac{1}{{\lambda }^4}}$$
Where I is the intensity of the light and $$\lambda$$is the wavelength of the light.

Sun rays are supposed to travel a longer path at sun rise and at sun set, as the sun will be at a longer distance from the earth’s surface. when compared to the mid day.
The red light has a longer wavelength and gets less scattered, thus, covers the longest distance and reaches the earth's surface during sunrise and sunset.
Sun will be at a nearer distance during mid day, thus VIBGYOR light reaches the earth surface and hence it appears white.

At sunrise or at sunset the sun appears to be reddish while at midday it looks white.

So, the correct answer is “Option A”.

Note:
The things to be on your figure tips for further information on solving these types of problems are:
Scattering and diffraction are two different phenomena. Scattering is a phenomenon in which the light scatters into different wavelengths, whereas diffraction is a phenomenon in which the light (wave) spreads around the obstacle.