How do human perceive the black color

Photoreceptor cells

Explanation:

The human eye and brain together translate light into color. Light receptors within the eye transmit messages to the brain, which produces the familiar sensations of color. ... Rather, the surface of an object reflects some colors and absorbs all the others. We perceive only the reflected colors thus, we have two types of photoreceptor cells, known as rods and cones. Cone cells deal in colour, while rod cells allow us to see in grayscale in low-light conditions, for example at night.

The color black is a not a reflection of colors, but an absorption, meaning that all the colors of the spectrum are absorbed by the object.

Explanation: "We see the color of an object because that object reflects “a color” to the eye. ... Black is not a color; a black object absorbs all the colors of the visible spectrum and reflects none of them to the eyes. The grey area about black: A black object may look black, but, technically, it may still be reflecting some light."

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.