In colder countries, glass walled houses are constructed to preserve the vegetation’s during the winter season. These are called Green Houses, which serve as effective heat-traps. This can be explained by Wien’s law.
We know from Wien’s law- “The wavelength corresponding to the maximum energy of emission is inversely proportional to the absolute temperature of the emitting body.”
Let λm be the wavelength corresponding to maximum radiant energy and the absolute temperature of the black body is T, then according to Wien’s law, λm ∝ 1/T.
Radiation from the sun being stronger in shorter wavelengths is transmitted by glass so that the temperature of the objects inside the green house is raised. As the temperature of the green house is not high, the radiation emitted by them is richer in longer wavelengths which are not transmitted by glass. Hence heat from the inside of the green house cannot escape by radiation so that the temperature inside remains greater than temperature outside. For this reason, plats, vegetables, seeds etc. can be grown and preserved easily.
