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A black body at 1227 °C emits radiation with maximum intensity at a wavelength of 5000 A. If the temperature of the body is increased by 1000 °C, the maximum intensity will be observed at

Asked in CBSE AIPMT 2006 · Wien's law and emissivity

• (1) 3000 A
• (2) 4000 A
• (3) 5000 A
• (4) 6000 A

Step-by-step solution

Why the other options are wrong

• (2) 5000-1000=4000: the 1000 of the temperature rise subtracted from the wavelength instead of being added to the temperature
• (3) comes from takes the peak wavelength to be a fixed property of the body; Wien's law moves it whenever the temperature changes
• (4) 5000+1000=6000: the same number added to the wavelength, which also shifts the peak the wrong way, since a hotter body peaks at a shorter wavelength

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