Spectral flux density

In spectroscopy, spectral flux density is the quantity that describes the rate at which energy transferred by electromagnetic radiation is received from a source, per unit area facing the source, per unit wavelength range. In SI units it is measured in W m^-3, though it is more practical to measure it in W m^-2 nm^-1 or W m^-2 μm^-1.

At any given wavelength "λ", the spectral flux density, "F_λ", can be determined by the following procedure:

*An appropriate detector of cross-sectional area 1 m² is pointed directly at the source of the radiation.

*A narrow band-pass filter is placed in front of the detector so that only radiation whose wavelength lies within a very narrow range, "Δλ", centred on "λ", reaches the detector.

*The rate at which EM energy is detected by the detector is measured.

*This measured rate is then divided by "Δλ" to obtain the detected power per square metre per unit wavelength range.

Spectral flux density is often used as the quantity on the y-axis of a graph representing the spectrum of a light-source, such as a star.

References

cite book
last = Green
first = Simon
authorlink =
coauthors = Mark Jones, S. Jocelyn Bell-Burnell, Barrie W. Jones, Robert J. A. Lamboourne, John C. Zarnecki
title = An Introduction to the Sun and Stars
publisher = Cambridge University Press
date = 2004
location = Cambridge
pages =
url =
doi =
id =
isbn = 0521837375