Chapter 2 — Exam Question 3
What is the electromagnetic spectrum?
Answer
Please refer to Figure 2.5.
The EM spectrum is the full range of EM energy radiated from an object
with a certain temperature (above 0
◦
Kelvin). It starts from cosmic rays and
gamma rays at short wavelengths, through x-rays, ultraviolet (UV), the visible
range, infra-red (IR), microwaves, TV and radio waves and electric power at
long wavelengths. For remote sensing purposes, the so-called ‘optical’ range is
the sub-range from x-rays to IR, which can be sensed and imaged. The visible
range includes Red, Green and Blue, which make together all the colours that
we can see with the naked eye.