Questions

Heat energy can be transferred by three major methods. They are 

1. Conduction,

2. Convection and

3. Radiation.

Conduction is the movement of heat through a substance by the collision of molecules

Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.

Radiation is the transfer of energy by means of photons in electromagnetic waves governed by the same laws. It occurs through a vacuum or any transparent medium.

According to Rayleigh's law, the intensity of scattered light varies inversely as the fourth power of its wavelength. Sunlight consists of seven colours. Of these, red has the maximum wavelength. During sunrise and sunset, the rays have to travel a larger part of the atmosphere because they are very close to the horizon.Therefore, light other than red is mostly scattered away. Most of the red light, which is the least scattered, enters our eyes. Hence, the sun and the sky appear red.

Adi Sankara