What are the main differences between photometry and radiometry?
Photometry measures light in terms of human visual response, focusing on visible wavelengths and luminosity. Radiometry measures all electromagnetic radiation, including visible, ultraviolet, and infrared, in terms of absolute energy without considering human perception.
How is photometry used in astronomy?
Photometry in astronomy is used to measure the brightness and intensity of stars and other celestial objects. It helps determine their properties such as distance, temperature, chemical composition, and variability. By analyzing light variations over time, astronomers can also study stellar phenomena like exoplanets' transits and variable stars.
What are the units of measurement in photometry?
The units of measurement in photometry are lumens for luminous flux, lux or lumens per square meter for illuminance, candelas for luminous intensity, and candela per square meter or nits for luminance.
How does photometry differ from spectrophotometry?
Photometry measures the intensity of light, typically within the visible spectrum, whereas spectrophotometry measures light intensity across various wavelengths, providing information on the light's spectral distribution.
How does the human eye's sensitivity impact photometric measurements?
The human eye's sensitivity impacts photometric measurements by giving more weight to the wavelengths of light to which it is most sensitive, particularly around the green region at 555 nm. Photometric measurements account for this sensitivity using the luminous efficiency function, which adjusts for human perceptual response rather than objective light intensity.