Radiometry is the study of how light, carried by electromagnetic waves made up of particles called photons, travels through space. It involves measuring and analyzing the energy (radiant energy) of these waves and their component particles.
- Radiometry studies the properties of electromagnetic radiation such as intensity, spectral distribution and polarization, and how light interacts with matter (absorption, reflection, and scattering).
- Electromagnetic radiation and the electromagnetic energy it transports can be described in terms of waves.
- Electromagnetic radiation (radiant energy) includes all wavelengths of light from radio waves to gamma rays.
- Electromagnetic radiation can be described in terms of photons and their properties.
- Energy: Photons have energy that depends on their frequency or wavelength. Higher-frequency photons have more energy than lower-frequency photons.
- Number: The number of photons in a given electromagnetic radiation depends on its intensity. Higher-intensity radiation has more photons than lower-intensity radiation.
- Direction: Photons travel in straight lines, but their direction can be changed by interacting with matter.
- Polarization: Photons can be polarized, which means that their electric and magnetic fields oscillate in a particular direction.
- Speed: Photons travel at the speed of light, which is approximately 299,792,458 meters per second in a vacuum.
- Radiometric techniques characterize the distribution of radiant power (transfer of energy per unit of time) in space.
- Radiant power, also known as radiant flux, is the amount of energy emitted by a source of electromagnetic radiation per unit of time. It is typically measured in watts (W) or in other units of power such as ergs per second (erg/s) or joules per second (J/s).
- While radiometry deals with electromagnetic radiation, photometry deals with the interaction of light with the human eye.