What is illumination? What units and devices are used to measure it? What are the laws of illumination?

First. This is a value that is expressed by the ratio of the luminous flux incident on a surface area to its area. 2) Measured either “lux” or “one lumen per square meter”. Measurements are made using a luxmeter or an exposure meter. The second is used more when photographing, and a luxmeter in all other cases. The first law of illumination: “cat” is equal to dividing “hippopotamus” by “tree” squared. Such abbreviations are conventionally taken and they mean: “cat” is the illumination of the surface, “hippopotamus” is the intensity of the light, “tree” is the distance between the source and the illuminated object. The next law: “cat” is directly proportional to the cosine of the angle of incidence of the rays.