The document discusses several key concepts relating to blackbody radiation: 1) A blackbody is an idealized object that absorbs all electromagnetic radiation falling on it without reflecting or transmitting any. 2) The purpose of the experiment was to measure the intensity of electromagnetic waves emitted by a blackbody as its temperature increases, and to use Wien's and Stephan Boltzmann's laws. 3) The experiment had many flaws and issues, resulting in unreliable data that did not match theoretical predictions.

1. By: William Lawrimore

2. Black Body idealized object that absorbs all electromagnetic radiation that falls on it. No electromagnetic radiation passes through it and none is reflected. Purpose of this experiment The purpose of this experiment is to measure the intensity of electromagnetic waves emitted by a black body as its temperature increases. Also to use Wien's law to find the max wavelength and use Stephan Boltzmann's law to calculate light intensity.

3. Week 1 Built / fixed flaws in the spectrophotometer. Week 2 Read instructions and tried to follow the calibration procedures (x1000). Week 3 Finally able to run the experiment with flawed results.

4. A set of independent displacements and/or rotations that completely describe the change in position of an object. Example – Particle in 3 dimensional space. 5 possible degrees of freedom (if the particle has structure). 3 dimensions of motion. 1 dimension of rotation (if particle has structure). 1 dimension of vibration (if particle has structure).

5. If the temperature of a system is known The average energy in each degree of freedom can be calculated. In 1845 John Waterston proposed that each medium of motion shared equally in the kinetic energy of a particle

6. In 1876 Ludwig Boltzmann proved Waterston’s theory to be correct. On average, the amount of energy contained in a degree of freedom is equal 1/2 kT. Where k is Boltzmann’s constant, and T is the temperature of the system in Kelvin.

7. Not Quite Right.  Problem: Each frequency of an electromagnetic wave had a designated degree of freedom. Frequency can increase almost infinitely. Each new frequency providing 0.5kT worth of energy. Called the U.V. catastrophe. Since light with a finite frequency cold have almost infinite energy. Everything in the upper frequencies would glow.

8. Most current and correct solution. Constrain light to only have certain amounts of energy. i.e. say light can only hold nhf energy where n is a non-negative integer, h is a constant and f is the frequency. This works because hf>>kT. So as an example 0.5kT = 0.001hf. However, the energy can only be 0 or 1 and 0.001 is much closer to 0 than 1.

9. Maxwell Planck - "There is no objectively defined reality out there, the universe seems to require us to interact with it before it can come into being". From a paper he wrote in 1900. In this publication he suggested that there was a relationship between the energy given off by a heated body and the frequency at which it vibrated.

10. Metal box Experiment. Assumed that vibration energy was not constant. Light energy instead was made up of small pieces. Planck called them “energy elements” later they were renamed as “quanta”. From this he was able to develop a formula for the entropy of a black body. From this formula Planck was able to discern that (epsilon) = hv. Where h is Planck’s constant of proportionality and v is the frequency.

11. There is an inverse relationship between the wavelength of the peak emission of a black body and its temperature. (lambda[max])=(b)/(Temperature). Where b Wien’s constant for displacement. 2.8977685 x 10^6nmK. Which is in nanometers x Kelvin. Developed this theory in 1893.

12. Observed how a cavity containing waves of light in a thermal equilibrium expanded adiabatically. Under compression or expansion the frequency of light and the temperature of the system changed proportionally.

13. Discovered that the thermal radiation given off by a black body was proportional to the surface temperature raised to the fourth power. (Thermal Radiation)=(sigma)(Surface Temp)^4. Sigma is yet another constant of proportionality, Stephan Boltzmann’s constant. 5.67 x 10^(-8)W/[(m^2)(T^4)].

14. Temperature (K) Maximum Wavelength (nm) 2168.697 1336.17 2247.493 1284.33 2364.360 1225.60 2435.428 1189.83 2610.712 1109.95

18. Originally couldn’t understand why graphs were flawed. The hopeful future engineer can’t build a simple experiment that came with instructions. Building flaw cased the data studio to ping graphs at 20% light intensity. Other graphs (not shown) were not even readable.

19. Many, many sources of error. The presenter. Spectrophotometer dysfunctional out of the box. Broken prism. Rotary Sensor. Ambient light. Extra radiation reached the sensor that was not from the black body lamp.