photo electric black body + solar (1 Viewer)

[Daveusdog]

Hey, can someone please explain very simply to me how the whole frequencies in the black body or wavelengths increase or whatever and how they escape the hole and why the graph has a peak...

Also can i please have some explainations for how the whole solar cell with the N type and the P type and the junction work. Where does the light hit etc.... what happens to electrons i just dont get any of it???
please help

 

[tennille]

A black body is a perfect emitter and absorber of radiation. The reason why the graph peaks is because energy is quantised (absorbed and emitted in little packets) instead of continuously. Classical physics stated that as the wavelength decreases, the energy radiated should increase indefinitely but this defied the law of conservation of energy.

The black body itself is like a cylinder (usually tungsten) which is heated in a vacuum by passing an electric current through it (like a light bulb). The cylinder contains a hole to make the black body cavity. The cavity emits more intense radiation than the cylinder walls.

Just imagine if you heat a piece of metal- first itll be a reddish colour, then as it gets hotter, it'll begin to emit visible light, then eventually uv light. That's similar to a black body.

I don't know if this helped you much but yeah. Sorry if it didn't.

I don't know how the solar cell works, though.

 

[tennille]

A black body is a perfect emitter and absorber of radiation. The reason why the graph peaks is because energy is quantised (absorbed and emitted in little packets) instead of continuously. Classical physics stated that as the wavelength decreases, the energy radiation should increase indefinitely but this defied the law of conservation of energy.

The black body itself is like a cylinder (usually tungsten) which is heated in a vacuum by passing an electric current through it (like a light bulb). The cylinder contains a hole to make the black body cavity. The cavity emits more intense radiation than the cylinder walls.

Just imagine if you heat a piece of metal- first itll be a reddish colour, then as it gets hotter, it'll begin to emit visible light, then eventually uv light. That's similar to a black body.

I don't know if this helped you much but yeah. Sorry if it didn't.

I don't know how the solar cell works, though.

 

[Jase]

um.. Well im not exactly sure what you're asking, but a black body emits radiation when it gets hot. When it gets hot, the atoms in it vibrate and produce electromagnetic waves. The frequency and wavelength of these waves are calculated by c = frequency x wavelength.

Wavelength changes only due to the temperature of the black body. The intensity changes due to wavelength. In classical physics, as the wavelength became really small, the intensity approached infinity, which is impossible. So Planck came along and introduced packets of light. The graph has a peak because that is the discrete limiting output of energy on a certain black body. (E = hf)

Well, there's two ways to look at photocells-
Firstly, theres an n-type layer of semiconductor material, which has a metal grid laid across it. Then in the middle is a junction. Below that is a p-type layer. Now the n-type layer is exposed to the sun, and the radiation knocks electrons out of that layer. The metal grid collects these photoelectrons, and also connects to the p-type, in a curcuit. The p-type 'gives' electrons to the n-type due to the electric field now created. Now a current flows and powers stuff.

the other way is with band theory. A photon of light hits the valence band, which excites an electron into the conduction band, and a current is produced.

 

[Daveusdog]

thanks for your help