Question

What is very valuable in terms of heat radiatin
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Answer 1

Answer:

certainly, energy can be transferred between bodies by em radiation of any frequency. Which part of the spectrum is mainly involved depends on the nature of the bodies. If they are not devices specifically designed to emit radiation then - in the temperature range we usually deal with, say below 3000° K - nearly all of the energy radiated by them is located in the infrared domain, i. e. it's thermal radiation (see Plank's black-body radiation law).

Of course, this is not true if we deal with devices like microwave ovens or mobile phones. If you want to estimate the increase of temperature in your body caused by a mobile phone you have to take the frequency band used for transmission into account.