2007 HSC Q27a) - Blackbody radiation curve (1 Viewer)

[superstar12]

"Scientists tried to explain observations of black-body radiation using classicalwave theory and then quantum theory. How does quantum theory satisfactorily explain black-body radiation?"

The marking comments said 'In the better responses, candidates linked quantum theory to problems with classical predictions.' In addition, For 3/3 marks, the marking criteria says:
- Describes a black body in terms of its features and radiation curve
- Links the shape of the curve to emission of energy in packets/quanta

I'm not really sure how Plank's hypothesis about quanta and E=hf explains the black-body radiation curve. Could someone shed some light on this for me? Exemplar response would be greatly appreciated

 

[mrpotatoed]

Where did you find a marking criteria for this? I thought they only exist for the most recent hsc papers... anyway

Classical physics predicted that the radiation emitted by a black body should continuously increase in intensity as wavelength absorbed became shorter. While the mathematical equations developed could accurately predict black body emissions for low energy, it did not match experimental evidence for higher energy. They predicted that the radiation emitted by a black body should continuously increase in intensity as wavelength became shorter, however this violated the conservation of energy as the total energy (area under graph) would be infinite. Experimental data instead showed that the graph peaked at UV, and then fell. Planck's hypothesis that energy released by a black body is quantised, and that the radiation is released in packets of energy proportional to the frequency produced mathematical equations that was accurate with experimental data.

A bit too long for a 3 marker

 

[InteGrand]

I'm not really sure how Plank's hypothesis about quanta and E=hf explains the black-body radiation curve. Could someone shed some light on this for me? Exemplar response would be greatly appreciated

To actually explain WHY this explains the black-body radiation curve is beyond the syllabus. All you need to know is THAT it explains it (which doesn't aid with understanding unfortunately). If you want some help with understanding why, check this thread for some explanations and links to explanations (requires heavy maths and physics, and none of this understanding is required for HSC Physics): http://community.boredofstudies.org/265/ideas-implementation/336155/uv-catastrophe.html

 

[Kaido]

Planck's hypothesis that energy released (and or absorbed) by atomic oscillators in a black body is quantised, and that this quantum of energy is given by E=hf; enabling Planck to derive a formula for the entire Black Body spectrum, which agreed with the experimental evidence. Thus, he had solved the 'UV catastrophe' concerning Black Body radiation, as predictions made by classical physics violated the law of conservation of energy.

Tbh, I think you only started answering the question from this part onwards. Preface is unnecessary

I made edits rofl, soz

 

[mrpotatoed]

Tbh, I think you only started answering the question from this part onwards. Preface is unnecessary

I made edits rofl, soz

ha, much better than mine