Question

what is the principle behind black and white photography?

Answer 1

When an image has a pure black point and a pure white point, with a variety of tones of grey in the image, the image is said to have higher contrast. The best amount of contrast in an image is certainly image-dependent, but most black and white images that have impact often have a strong amount of contrast.

Answer 2

The following reaction of decomposition takes place of silver halides which are used in black and white photography.

2AgBr(s) ➡ 2Ag(s) + Br2(g)

In this reaction silver bromide gives silver metal and bromine gas in the presence of sunlight.

Hope it helps!!