Question

what was it that Plank explained about radiation of hot object ?
why the scientists before Plank thought that hot objects must emit UV light and must disappear ?

Answer 1

there was no theory of perfect black body before plank! and a perfect black body emits radiations and does not disappear!

Answer 2

would like to knw why they thought the hot body radiation increases in frequency and reaches UV... im in grade 12 studying atomic models. and got stuck at E=hf concept.. .

Answer 3

his equation E = hf says the same thing. if we increase heat energy E, the emitted frequency must increase as h is constant

Answer 4

if we keep heating, the emitted frequency must reach UV. whats so different about his equation compared to the thinking of scientists before him

Answer 5

@sara12345 all objects with a total intensity that is proportional to the fourth power of the Kelvin temperature, emit radiation. At normal temperatures, intensity is low, and thus we don't necessarily notice electromagnetic radiation. However at higher temperatures, there is plenty of infrared radiation and we can actually feel the heat if we get too close to the object. At extremely high temperatures objects will glow, such as a stove or a filament of a light bulb. The temperatures are proportional to the intensity of the electromagnetic radiation emitted and the amount of radiation only increases at higher and higher frequencies. A body that absorbs all of the radiation appears totally black under reflection when illuminated from the outside, and such a body is known as a blackbody. The radiation emitted from such a body is called blackbody radiation.

Planck's hypotheses proposed that each atom within a molecule oscillates with energy which is a multiple of the minimum frequency of oscillation. Thus\[E =hf\]where\[h =6.626\times 10^{-34} Js\]is called Planck's constant. @sara12345 please note that the energy of the vibrating molecules can only be some whole number multiple of hf. Example\[E =nhf\]where n = 1, 2, 3, 4, 5, ..., where n is some quantum number (discrete number). Discrete means integer values.

Answer 6

a hot body can emit higher frequencies also in uv range is it if it is heated enuf ?

Answer 7

true for some metals! depends on the work function!