# Ultraviolet Light

## Vocabulary

### absorption spectrum

amount of light absorbed by a compound as a function of the wavelength of light

### color

phenomenon of light (such as red, green, or blue) or visual perception that enables someone to differentiate otherwise identical objects

### conjugated diene

diene consisting of two double bonds that are separated by one single bond

### electromagnetic spectrum

entire range of electromagnetic waves, defined by their energy, wavelengths, and frequencies

### energy

capacity to do work

### frequency

number of oscillations of a wave that occur in a given period of time, usually a second, measured in hertz (Hz)

### highest occupied molecular orbital (HOMO)

highest energy level that is occupied by electrons

### lowest unoccupied molecular orbital (LUMO)

lowest energy level that is not occupied by electrons

### ozone layer

atmospheric layer at heights of about 20 to 30 miles (32 to 48 kilometers), normally characterized by high ozone (O3) content that blocks most solar ultraviolet radiation from entry into the lower atmosphere

### period

amount of time required for one vibrational cycle, equivalent to the inverse of frequency

### ultraviolet light

light wave situated beyond the visible spectrum at its violet end and consisting of radiation having a wavelength shorter than wavelengths of visible light and longer than those of X-rays

### ultraviolet spectrometer

device that measures ultraviolet (UV) electromagnetic waves

ability to see

### wavelength

distance between two identical parts of a wave

### Woodward-Fieser rules

set of empirically derived rules that predict the wavelength of the absorption maximum ($\lambda_{\rm max}$) in an ultraviolet–visible spectrum of a given substance