Far Infrared Rays (FIR), a part of natural sunlight having the longest wavelength, cannot be seen with the naked eye.

远红外线(区)，自然有阳光的波长最长的一部分，不能用肉眼看到。

youdao

Far Infrared Rays (FIR), a part of natural sunlight having the longest wavelength, cannot be seen with the naked eye.

远红外线(区)，自然有阳光的波长最长的一部分，不能用肉眼看到。

youdao