The electromagnetic spectrum is generally divided into seven regions, in order of decreasing wavelength:
1. Radiowaves (103 m)
2. Microwaves (10-2 m)
3. Infrared rays (10-5 m)
4. Visible rays (0.5 × 10-6 m)
5. Ultraviolet rays (~ 10-8 m)
6. X-rays (~ 10-10 m)
7. Gamma rays (~ 10-12 m).