Decay rate describes how quickly the amplitude of a wave or oscillation diminishes over time. In physics, this concept applies to everything from a swinging pendulum losing energy to friction, to the exponential decay of radioactive particles, to the damping of electromagnetic waves in a medium. It quantifies how a system returns to equilibrium after being disturbed.
History
The mathematical formalism of exponential decay was established in the 17th century, but its application to wavedamping and particle physics developed through the 19th and 20th centuries, notably with Rutherford's work on radioactivity.
How it works
The decay rate is typically expressed as a constant that appears in an exponential function, such as A(t) = A₀ e^(-λt), where λ is the decay rate. A higher λ means faster decay. The mechanism behind it varies: for mechanical oscillations, it's often friction or air resistance; for particles, it's quantum mechanical processes like spontaneous emission or nuclear instability.
In practice
Decay rates are used in medical imaging (e.g., PET scans), in dating archaeological artifacts via carbon-14, and in designing shock absorbers and damping systems for buildings and vehicles.
Fun fact
The decay rate of a pendulum in a vacuum is so small that it can swing for hours, but in air, it loses energy much faster due to air resistance.
Units by system: SI: per second · CGS: per second · Planck: per planck time · natural: per second
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