The electromagnetic spectrum

What is the wavelength of light to which the human eye is sensitive? Answer: 0.00000040 - 0.00000070 meters. Bah! Use scientific notation: meters.
A lot of other phenomena are identical to light except the wavelength is different.
Transparency, Figure 6-5.
Longer wavelength: infrared (IR), microwave, radio waves.
shorter wavelength: ultraviolet (UV), X-rays, Gamma rays.

How is electromagnetic radiation produced? A; lots of ways. One important way is blackbody radiation. Hot objects emit light. Hotter objects emit more light.
illustration/demonstration with light bulb.

To talk about production and characteristics of light, we need to introduce a defintion: a spectrum. Spectrum is intensity of light versus (``is a function of'', in fancy mathematical language) wavelength.
Graph of intensity of light versus wavelength.