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A good start to this discussion is what creates a rainbow? White light, which is a mixture of all the different
colors of light, is broken into its component colors by small water droplets in the atmosphere. The droplets
are essentially acting as a prism, which will also divide light into its component colors.

Visible light is a form of electromagnetic radiation, or electromagnetic waves. Other forms of
electromagnetic radiation include:

• radio waves
• infrared light
• ultraviolet light
• x-rays
• gamma rays

All of these forms of electromagnetic radiation are oscillating waves in the electric and magnetic fields.
These fields oscillate from a negative value, to zero, to positive value, and then back through zero to
negative again and so on. Different colors of light and different forms of electromagnetic waves have
different values ofwavelength and frequency.

We often think of light and other electromagnetic radiation as having wavelike properties. Light will also
display particlelike properties. Light comes in discrete packets called photons, which can be thought of
as particles of light. When a photon of the correct amount of energy strikes an electron in an atom, the
electron will absorb the energy and jump to a higher energy level. When the electron jumps back down to
a lower energy level, it will emit a photon with the appropriate amount of energy.

These absorbed and emitted photons are the basis for spectroscopy as a way of finding the chemical
composition of something. The absorbed and emitted photons cause spectral lines when the light passes
through a prism and is broken into its component colors. Because each type of atom has its own unique
set of energy levels, each type of atom has its own unique set of spectral lines. Scientists use these
spectral lines to identify the chemical composition.

What Happens When Light Interacts with Matter?

Unlike most other types of waves, light and other electromagnetic waves propagate in a vacuum. When a
light wave encounters some medium, several things can happen. Depending on the type of medium, the
possibilities include:

Refraction

Reflection

Absorption

Scattering

Diffraction

Sometimes more than one of these will occur. For example, a beam of light might strike a glass lens, and
some of the light will be refracted while some is reflected.

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