This document discusses black-body radiation. It defines a black-body as an ideal absorber of incident radiation that reflects no energy. It then covers the theory of black-body radiation, including Rayleigh-Jeans law, Planck's law, Wein's displacement law, and Stefan-Boltzmann law. These laws describe how a black-body's wavelength of peak emission shifts to shorter wavelengths with increasing temperature and how the total energy emitted increases rapidly with rising temperature. The document concludes that as temperature increases, the peak wavelength decreases and total emitted energy under the curve increases, getting infinitely close to but never touching the x-axis.

1. NAME: RAHIDUL SEKH
ROLL NO.: 60
UNIVERSITY ROLL NO.: 234060212
STREAM: IT
SECTION: A
BLACK-BODY RADIATION

2. • Contents of this PPT
▪ Introduction
▪ Definition
▪ Theory
▪ Conclusion
▪ Reference

3. INTRODUCTION OF BLACK-BODY
• Black-Body is important in thermal radiation theory and practice.
• The ideal Black-Body notion is important in studying
electromagnetic radiation transfer in all wavelength bands.
• The Black-Body is used as a standard with which the absorption of
real bodies is compared.

4. • DEFINITION OF A BLACK-BODY
A Black-Body is an ideal body which
allows the whole of the incident
radiation to pass into itself(without
reflecting the energy) and adsorbs
within itself this whole incident
radiation (without passing on the
energy). The property ia valid for
radiation corresponding to all
wavelengths and to all angels of
incidence. Therefore, the Black-Body
is an ideal absorber of incident
radiation. A basic Diagram of a Black-Body

5. • THEORY
1. Black-Body radiation Law –(1)
The Rayleigh-Jeans Law.
 It agrees with experimental
measurements for long wavelengths.
 It predicts an energy output that diverges
towards infinity as wavelengths grow
smaller.
 The failure has become known as the
ultraviolet catastrophe.
2πckT
I(λ,T) =--------
λ4

6. o Ultraviolet Catastrophe:
 This formula also had a problem. The
Problem was the λ term in the
denominator.
 For large wavelengths it fitted the
experimental data but it had major
problems at shorter wavelengths.

7. 2.Black-Body Radiation Law (2)
Planck`s Law
We have two forms. As a function of
wavelength.
And as a function of frequency
Planck`s Law gives a distribution that
peaks at a certain wavelength , the peak
shifts to shorter wavelengths for higher
temperatures , and the area under the
curve grows rapidly with increasing
temperature.

8. 3.Black-Body Radiation Law (3)
Wein`s Displacement Law
• It tells us as we heat an object up,its color
changes from red to orange to white hot.
• Formula & notation
λ max=b/T
Where, λ is Wavelength.
b is Wein`s constant.
T is Temperature.

9. Comparison of Rayleigh-Jeans Law with Wien`s Law and Planck`s Law , for a body of temperature.

10. 4. Black-Body Radiation Law (4)
The Stefan-Boltzmann Law
• Gives the total energy being emitted at all
wavelengths by the blackbody (which is the
area under the Planck Law curve).
• Explains the growth in the height of the curve as
the temperature increases. Notice that this
growth is very abrupt.
j=σT4
• Sigma = 5.67 * 10 J s² m² K, Known as the
Stefan- Boltzmann constant.

11. • CONCLUSION
As the temperature increases, the
peak wavelength emitted by the
black body decreases.
As temperature increases, the
total energy emitted increases,
because the total area under the
curve increases.
The curve gets infinitely close to
the x-axis but never touches it.

12. • REFERENCE
• A black body is a theoretical object that absorbs 100% of the radiation that
hits it. Therefore it reflects no radiation and appears perfectly black.
• Roughly we can say that the stars radiate like blackbody radiators. This is
important because it means that we can use the theory for blackbody
radiators to infer things about stars.
• At a particular temperature the black body would emit the maximum
amount of energy possible for that temperature.
• Blackbody radiation does not depend on the type of object emitting it. Entire
spectrum of blackbody radiation depends on only one parameter, the
temperature, T.