Key relationship
Pnet=εσA(T⁴−Ts⁴); λmaxT=2.89777×10⁻³ m·K; spectrum follows Planck law.
Physics · Class 11
Shift a blackbody spectrum
Hotter bodies emit much more power and peak at shorter wavelengths. Stefan law controls total power through T⁴; Wien law locates the spectral peak through 1/T. The curve uses Planck spectral radiance.
Open the interactive experiment →Shift a blackbody spectrum
வெப்பநிலை அதிகரிக்கும்போது கதிர்வீச்சு ஆற்றல் T⁴க்கு ஏற்ப அதிகரிக்கும்; உச்ச அலைநீளம் குறையும்.
Key notes, relationships and model limits
Remember
Hotter bodies emit much more power and peak at shorter wavelengths. Stefan law controls total power through T⁴; Wien law locates the spectral peak through 1/T. The curve uses Planck spectral radiance.
Common trap
Stefan and Wien laws require temperature in kelvin.
Model limits
Uniform greybody with wavelength-independent emissivity; blackbody spectrum times ε. Ambient is a surrounding enclosure; no convection or conduction.
What you will learn
Connect spectral shape, peak location and total radiation power.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
At 1200 K, λmax=2.89777×10⁻³/1200=2.415 μm. A 0.1 m² blackbody in 300 K surroundings radiates net about 11712 W.
Why this matters
The model connects shift a blackbody spectrum with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
If absolute temperature doubles, how does the peak wavelength change?
- It doubles
- It halves
- It stays fixed
Read the explanation
Wien displacement law keeps λmaxT constant.
Course connection: Class XI Chapter 10. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.