Photometer means the measuring instrument. Photometry means measuring light intensity and the amount of illumination. The names of light measurements or photometers are also often used in the field of astronomy. Photometry compares different light intensities in the human eye. Photometry irradiation utilizes radiometers in power units or as energy. When measuring on photometers, the measured lamp is compared to any standard lamp. The most common and widely used method is to examine the distance to any display until both lamps provide the same intensity of illumination. The next thing to do is to take the square of the distance from the screen. Because this will be light intensity. Sometimes the screen is not used. Instead, a paper with an oil stain in the middle is used. This means that when the oil stain does not appear, both sides will have the same amount of illuminated paper.
Photometry examines their magnitude depending on the perception of light. Light emits a temperature that can be seen with some special tools. The power carried by light is therefore a magnitude dependent on light. Because our eye is selective, our eye only sees the wavelengths between 0.4-0.8 micrometers.
The light flow F defines the light energy that our eye perceives in unit time. If a light source emits this light flow, the light intensity of that source I is determined by a current element. The unit of light intensity is candela (cd). This unit defines the light flow unit, the light unit per square meter and the lighting unit. Our eye can see 10 to 13 light flow units.
Photons can be displaced by 300,000 kilometers, ie, the rate at which light emits in space per second. Their energy is equal to the product of the f frequency of the radiation and the Planck constant. The speed of the photon in equilibrium should be zero. Mc2 = hf defines the relative mass of the photon. The amount of motion of this particle is determined by the Compton experiment.