• Entry
• Entries A-Z
• Subject Index

• RADIATION IS ENERGY transmitted by electromagnetic waves. Electromagnetic waves travel at the speed of light (when passing through a vacuum) and have a characteristic wavelength, λ, which is inversely proportional to their frequency, v, by

where c is the speed of light. Electromagnetic radiation is conceptualized in contemporary theory both as a wave and as a stream of particles called photons (this dual approach is referred to as wave-particle duality). The energy of any photon, E, of radiation is inversely proportional to the wavelength by

where h is Planck's constant. This relationship allows us to order electromagnetic waves from high energy/short wavelength (for example, x-rays), to low energy/long wavelength (for example, radio waves). The resulting progression is referred to as the electromagnetic spectrum (Figure 1). The visible ...

• [0-9]
• A
• B
• C
• D
• E
• F
• G
• H
• I
• J
• K
• L
• M
• N
• O
• P
• Q
• R
• S
• T
• U
• V
• W
• X
• Y
• Z