What is Radiometry: Definition and 20 Discussions

Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which characterize the light's interaction with the human eye. The fundamental difference between radiometry and photometry is that radiometry gives the entire optical radiation spectrum, while photometry is limited to the visible spectrum. Radiometry is distinct from quantum techniques such as photon counting.
The use of radiometers to determine the temperature of objects and gasses by measuring radiation flux is called pyrometry. Handheld pyrometer devices are often marketed as infrared thermometers.
Radiometry is important in astronomy, especially radio astronomy, and plays a significant role in Earth remote sensing. The measurement techniques categorized as radiometry in optics are called photometry in some astronomical applications, contrary to the optics usage of the term.
Spectroradiometry is the measurement of absolute radiometric quantities in narrow bands of wavelength.

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  1. I

    I Radiant Intensity from Radiant Power and Intensity Distribution

    Consider the infrared led TSAL7600 which has the following properties: $$ \Phi = 35 mW $$ $$ I_e = 25 mW/sr $$ The half angle is ## 30^\circ ## and: $$ I_r(\theta) = cos^{4.818}(\theta) $$ is a good approximation for the relative radiant intensity. However, finding the actual radiant...
  2. R

    Classical Radiometry & Sensing Course: Find Syllabus Here

    This course is teaching a lot of stuff I'm interested in, which is radiometry and sensing. I don't want to email the instructor as I am not a student at this school, so it would just seem like I'm some nosey nobody. Does anybody have any idea of what they are using, or something similar to what...
  3. R

    Programs What graduate major deals the most with radiometry?

    I'm currently a sophomore physics major in undergraduate. I'm doing physics because I want my undergrad education to be really general. I want a goof foundation. What I'm really interested in is radiometry, which I believe is like optics but for all wavelengths, not just visible ones. I want to...
  4. Nima_khademi

    Calculating a distributed IR source radiant flux

    Hello everyone! does anybody know How can I calculate a distributed radiant flux of an IR source in a space? Is there any software or something?
  5. M

    I How does the inverse square law apply to a focused detector?

    I am interested in evaluating light intensity variation in a digital image. A colleague wants to apply an inverse square law correction to account for distance variation. I am trying to justify that in this case, the inverse square law does not apply. Treating each pixel as a detector, it has...
  6. R

    Mathematics necessary for Radiometry, Photometry, Thermodynamics

    What are the math concepts I have to learn for Radiometry, Photometry and Thermodynamics (all Calculus-based) as applied in building science (engineering, architecture, etc.). I'm almost done with Multivariable Calculus and I'm aware that MV Calculus is necessary, but what specific calculus...
  7. R

    Learning Radiometry, Photometry, Optics, Thermodynamics, ....

    Learning Radiometry, Photometry, Optics, Thermodynamics, Fluid Mechanics(Statics & Dynamics) with great resources. I'm looking for resources for understanding the topics above. I prefer video tutorials as opposed to books but I couldn't find any video resources on Photometry and Radiometry (I...
  8. M

    A Irradiance distribution of projected beam

    Hey folks, I'm having a little bit of trouble shaking the rust off of my radiometry. I'm projecting a circular beam of some known divergence and power onto a surface angled relative to the center of the beam. Say holding a flashlight, with a cone of half angle θ, at my waist some height h off...
  9. T

    B How are initial radioactive isotope quantities assumed?

    I'm stuck on this idea. How are initial radioactive isotope quantities assumed in radiometric dating? There are current abundances for all isotopes, but wouldn't these abundances have been different in the past (much higher)? I honestly can't grasp how radioactive isotopes with short half lives...
  10. synMehdi

    Antenna signal amplification

    I have an Antenna that receives signal coming from a wide band of distances, 10-2000 meters from a 10mW transmitter. I am working with 868 MHz band. What is the cheapest method ( or cheapest circuit ) to amplify this signal with an Automatic Gain Control LNA so that the received signal stays...
  11. V

    Radiometry, photocurrent in optics simulation

    Hi all, I have to estimate a photocurrent produced in the following simulation setup. Photodiode (detector) and LED (spaced 2cm) lie on one axis, oriented toward a wall (radiometer film) which is parallel to the axis and at a distance of about 10cm from the axis. How much photocurrent would an...
  12. J

    Buy a Radiometry Textbook for 0-10 Miles Wave Generation

    I want to send radio waves through distances of 0 to 10 miles, maybe even hundreds of miles eventually. What book should I buy to educate myself? I am not really interested in doing complicated things with electricity unless it translates directly into something which will improve the...
  13. P

    Measurement of irradiance of 2 beam interference

    Hi, I have an experiment set up to get two beam interference fringes. I would like to know how I could measure the actual amplitude of the irradiance from the experiment. I have with me a power meter and a CMOS camera. How can I go about this? Thank you
  14. mishima

    Good text or online source on Radiometry?

    I'm looking for a good text or online source that can take me through radiometry at an undergraduate level. I'm interested in drill type problems that can help me sort out the different quantities intensity, irradiance, exitance, radiance and their spectral counterparts. Also, solid angle vs...
  15. J

    What Does a 1cm Detector Record with a 100W Non-Lambertian Light Source?

    Homework Statement If the light source in figure 12.1 (see figure below) of the Warren Smith text is replaced by a 100W light bulb, and the lens aperture is 20cm, what would the 1cm detector at point E record? Assume all other values are the same, and the light bulb is not Lambertian...
  16. N

    Radiometry: Spectral Irradiance, Irradiance & Average Irradiance

    Hi, can someone tell me the difference between spectral irradiance, irradiance, and average irradiance? Thanks!
  17. D

    About radiance equation in Radiometry

    Homework Statement According to some pages on web, differential formula for calculating radiance L is : L = d2P / ( dA*cos(a)*dw) L : radiance P : power flux A*cos(a) : projected area w : solid angle Please tell me why does power P has derivaties two times d2P ? Homework...
  18. H

    What is the Exitant Radiance from a Lambertian Plate on a Cloudy Day?

    The exercise i have is as follows: A flat plate (measuring 0.5 meter by 0.5 meter) is placed on the highest mountain in the landscape, exactly horizontal. It is a cloudy day, such that the sky has a uniform radiance of 1000 W/ m^2 sr. The plate has a uniform Lambertian reflectance p=0.4...
  19. mnb96

    Understanding Radiometry: Calculating Radiance at Point P (0,0,0)

    Hello, assuming the definition of radiance in http://web.cs.wpi.edu/~emmanuel/courses/cs563/write_ups/chuckm/chuckm_BRDFs_overview.html" , I want to compute the radiance at the point P=(0,0,0) lying on the xy-plane, given a point-source of light at (0,0,1). The angle \theta in this scenario...
  20. A

    Thermal imaging and radiometry

    Can a thermal imaging camera detect a body that is cooler than the detector? Or does the temperature of the detector put an absolute floor on the temperatures of objects that can be detected? How do radiometers detect radiating bodies that are lower temperature than the radiometer? Or does...