Question

In places of hot climate, it is advised that the outer walls of houses be painted white. Explain.

Answer 1

We know that the temperature of a body is increased if the wavelength of the light is absorbed. A black body absorbs all the wavelengths of light and converts them into heat energy.

Complete answer:
White-surfaced objects reflect more heat and absorb less. Less heat from outside will also reach the building. White light is a combination, in approximately equal proportions, of all colors. White objects look white because all the visible light wavelengths that appear on them reflect back, so that the light still appears white to us. On the other hand, color objects only reflect some of the wavelengths; they absorb the remainder.

The more light an object absorbs, as light is energy, the more heat is absorbed. Black absorbs the most heat if you consider it a pigment. All wavelengths of light are reflected by a black object and reflect none. On the other hand, objects which are white reflect all wavelengths of light and thus absorb the least heat.

Additional Information:
White light: White light is nothing but daylight that's colorless. This includes at equal intensity all the wavelengths of the visible spectrum. Simply stated, electromagnetic radiation is considered white light for all the wavelengths in the visible range of the spectrum that appear white to the eye.

Note:
The following colors are used to render white light: red, orange, yellow, green, blue, indigo and violet. Each color light has a wavelength of its own.
Red light has the longest wavelength, and the shortest wavelength is violet light. However, the violet light has the highest energy while the red light has the lowest energy.