When exposed to ultraviolet, some substances, such as minerals, glow in characteristic visible wavelengths, a process called this?

• Correct Answer: pigment
• plasma
• chemical reaction
• fluorescence

Explanation: When exposed to ultraviolet, some substances, such as minerals, glow in characteristic visible wavelengths, a process called fluorescence. So-called black lights emit ultraviolet to cause posters and clothing to fluoresce in the visible. Ultraviolet is also used in special microscopes to detect details smaller than those observable with longer-wavelength visible-light microscopes. Things Great and Small: A Submicroscopic View of X-Ray Production X-rays can be created in a high-voltage discharge. They are emitted in the material struck by electrons in the discharge current. There are two mechanisms by which the electrons create X-rays. The first method is illustrated in Figure 24.18. An electron is accelerated in an evacuated tube by a high positive voltage. The electron strikes a metal plate (e. , copper) and produces X-rays. Since this is a high-voltage discharge, the electron gains sufficient energy to ionize the atom.

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