When Light Hits an Object

When a light wave hits an object, what happens to it depends on the energy of the light wave, the natural frequency at which electrons vibrate in the material and the strength with which the atoms in the material hold on to their electrons. Based on these three factors, four different things can happen when light hits an object:

• The waves can be reflected or scattered off the object.
• The waves can be absorbed by the object.
• The waves can be refracted through the object.
• The waves can pass through the object with no effect.

And more than one of these possibilities can happen at once.

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• Transmission - If the frequency or energy of the incoming light wave is much higher or much lower than the frequency needed to make the electrons in the material vibrate, then the electrons will not capture the energy of the light, and the wave will pass through the material unchanged. As a result, the material will be transparent to that frequency of light.

Most materials are transparent to some frequencies, but not to others. For example, high frequency light, such as gamma rays and X-rays, will pass through ordinary glass, but lower frequency ultraviolet and infrared light will not.

You can read more about what makes glass transparent on this page.