As a black body gets hotter, the wavelength at which it radiates most strongly
Correct answer: B. gets shorter
- A. gets longer
- B. gets shorter
- C. stays the same
- D. becomes infinite
Explanation
Wien's displacement law says the peak wavelength is inversely proportional to absolute temperature, which is why heated iron glows dull red and then white as it gets hotter. The same law lets astronomers deduce a star's surface temperature from its colour. The total power radiated rises even faster, as the fourth power of temperature.
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Quantum theory treats electromagnetic radiation as packets of energy called photons, with energy proportional to frequency through E equals hf. The topic covers Planck's hypothesis, photon momentum, the photoelectric effect, threshold frequency, work function and wave particle duality, distinguishing quantised energy exchange from classical continuous radiation.
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