The Photometry

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Today Let we all know the interesting informations about
" Photometry “

It is defined as the term that provides the measurement of light, as recognized by the eye of a human being.
This measurement deals with measurements associated with psychophysical attributes' of the energy of electromagnets that come under the visibility ranges of human eyes.
However, the concept of photometry is quite different from radiology as radiology deals with the measurements associated with radiations from the optics.
In dealing with this concept of photometry, the term luminous holds much significance.
Definition of photometry
• In simpler terms, photometry can be stated as the measure of the brightness of light that is noticed through the human eye.
• However, the concept of photometry arrived 2000 years ago at the time when the famous Greek astronomer, named Hipparchos was able to classify stars into six brightness.
• In modern times, photometry is the powers of radiance that are noticed at each wavelength.
• This wavelength is weighted by function luminosity based on the brightness sensitivity of humans.
What is a Photometer?
The term photometer has arrived from the root word, photo that means light, and this apparatus is used for measuring the interaction that is conducted when the light interacts with materials of reflections.
It device is also used to conduct several fields of studies with the notion of photometry.
This device helps in measuring the strengths that are conveyed from the electromagnetic radiations ranging between infrared to ultraviolet radiations .
These ranges also include the visible part present within the electromagnetic spectrum.
Moreover, it works by converting the light energy into current electricity, with the usage of photoresistors, photodiode and photomultiplier.
However, a photometer is used to measure certain parameters, that includes, the notion of illuminance, irradiance, aspect of absorption of light, fluorescence, reflection of light, luminescence, the notion of phosphorescence and lastly, the phenomenon of scattering of light.
Types of Photometer
There are two types of photometers used to measure the brightness of light, the first one is the spectrophotometer and the second one is the filter photometer.
The spectrophotometer uses a monochromator, to perceive the monochromatic light that is defined by one wavelength The monochromator is constructed with the help of a prism or grating.
On the other hand, a filter photometer uses optical filters to provide monochromatic lights.
Applications of photometry
The highly sensitive types of photometers are used for effective evaluation of the contrast ratios associated with the tubes of cathode rays, displays of liquid crystals and also of the displays flat panels .

The detectors (eye, photographic emulsion, photomultiplier, photodiode and charge-coupled device) are described.

Color systems in use in astronomical photometry are introduced, and the planning, the observational and reduction techniques are described.


Finally, some advice for the purchase of photometers and CCD cameras is given.

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