Consider the figure below. In the figure, the left image shows Io in visible lig

Question

Consider the figure below. In the figure, the left image shows Io in visible light, while the right image shows Io in the infrared. In the visible-light picture, the black spots are volcanos that are still active or have recently gone inactive. In the infrared picture, the bright spots are active volcanos. Which color in the infrared picture (blue, green, orange, red, or white) represents regions with the highest temperatures? Briefly explain your reasoning. The infrared picture was obtained when only part of Io was in sunlight. Based on the colors shown over Io's surface as a whole, which part of the surface was in sunlight (the left side, the right side, or only the peaks of the volcanos)? Briefly explain your answer.

Explanation / Answer

a) White colour in the infrared picture represents high temperature regions. The reason is the IR picture is the result of the emitted IR radiation when it is activated by an electromagnetic radiation. Infra red radiation is emitted by a body due to the atomic and molecular vibrations. If a body is colder, then the energy of that body is not sufficient to stimulate the atomic and molecular vibrations and thus, the IR radiation emitted by the cold body is of lower frequency. Thus, the cold body emits higher wavelength. As the object becomes hotter, the vibrations of atoms and molecules increase and thus the object with high temperature emits an IR radiation of higher frequency or lower wavelength. Thus the hotter regions can emit high enrgy of IR radiation which are represented by white spots.

b) As already discussed, the temperature of a body decides the emitting IR frequency or wavelength. Thus, the regions of high temperature represents the regions emitting lower wavelength of IR radiation which exhibit brighter colours. And the darker regions have low temperatures and so exhibit higher wavelengths of IR radiation and so be represented by darker colours. As seen in the image, only the peaks of the volcano's are having bright coloured display, it can be concluded that the sunlight is present over those areas.

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