They can also radiate farinfrared ray (FIR) energy of varying frequencies, which is something ordinary people can not do.
它们还可以辐射远红外线不同频率(区)的能源，这点是一般人做不到的。
2
FarInfrared 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。
3
In the high efficiency and small signal region, we investigate theoretically the efficiency enhancement mechanism of farinfrared free electron laser (FIR-FEL) with a reverse tapering waveguide.