Planck's Formula - Help undressing the question needed

  • Thread starter Thread starter Brewer
  • Start date Start date
  • Tags Tags
    Formula
AI Thread Summary
To plot Planck's formula for black body radiation, focus on the wavelengths where noticeable intensity occurs, particularly in the visible and infrared spectrum. The peak of the intensity distribution should ideally be set at the infrared edge of the visible spectrum to represent the temperature at which an object glows red hot. While the peak may appear orange or yellow to the human eye, the key is to identify the wavelength corresponding to the infrared threshold. This approach ensures that the graph accurately reflects the thermal radiation emitted by hot objects. Understanding these points will help in effectively visualizing and interpreting Planck's formula.
Brewer
Messages
203
Reaction score
0
I have a question that asks me to plot Plancks forumla for the wavelength dpendence of the intensity of black body radiation, and to use it to obtain an estimate for the temperature at which an object glows red hot.

Now I know Planck's formula (or its written in front of me), but I don't know what band of wavelengths I should plot. The EM spectrum? Other random wavelengths?

And for the red hot bit, is that the point at which the peak of the plot goes over a certain wavelength? The infra red end of the spectra?

Any help would be appreciated.
 
Physics news on Phys.org
Plot the portions of the spectrum that contain noticeable intensity ...
for a Temperature at which there's noticeable intensity in the "red".

The question author probably expects you to use a Temperature at which
the PEAK of the distribution is red (for whatever variable your equation is in)
- but this would appear orange-hot, with significant orange and yellow -
I would rather set the peak at the infrared edge of visible ...
even better, set the high-f inflection point at the infrared edge of visible.

[just because HUMANS can't see it , doesn't mean it isn't worth graphing!]
 
So it is the point at which the peak of the graph is in the infrared part of the spectrum then?
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top