The uncertainty principle
- 2. NAME - SUMIT KUMAR DAS CLASS ROLL NO.- 11/ME/14 WBUT ROLL NO.- 14800711061 REGISTRATION NO.- 11148011404
- 3. Before starting I would like to take this opportunity to express my sincere thanks to respected “ SIR ” for giving me this project… Apart from that I also want to thank my FRIENDS for helping me throughout the project with his inputs..
- 4. Uncertainty principle was stated by Werner Karl Heisenberg in 1927. This principle gives a very vital relation momentum and position of an object. This principle states that the position and momentum of a particle cannot be simultaneously measured with arbitrarily high precision. There is a minimum for the product of the uncertainties of these two measurements.
- 5. Continued……….. •Hence the formula for the uncertainty principle is as follows:-
- 6. The German physicist Werner Heisenberg (1901-1976) received the Nobel Prize in physics in 1932 for his work in nuclear physics and quantum theory. The paper on the uncertainty relation is his most important contribution to physics. In 1927, Heisenberg stated his uncertainty principle that a particle's momentum and position cannot both be determined.
- 7. This means that subatomic events have to be predicted using probabilities. He was a very talented and intelligent student. Heisenberg impressed his teachers with his ambition and brilliance. He never produced other grades than straight A's, except on one occasion: During his doctorate, professor Wien of the university of Munich gave him an F in experimental physics, because he handled the laboratory equipment clumsily.
- 8. In the world of very small particles, one cannot measure any property of a particle without interacting with it in some way This introduces an unavoidable uncertainty into the result One can never measure all the properties exactly Werner Heisenberg (1901-1976)
- 9. Shine light on electron and detect reflected light using a microscope Minimum uncertainty in position is given by the wavelength of the light So to determine the position accurately, it is necessary to use light with a short wavelength
- 10. By Planck’s law E = hc/l, a photon with a short wavelength has a large energy Thus, it would impart a large ‘kick’ to the electron But to determine its momentum accurately, electron must only be given a small kick This means using light of long wavelength!
- 11. Use light with short wavelength: accurate measurement of position but not momentum. Use light with long wavelength: accurate measurement of momentum but not position.
- 12. The more accurately you know the position (i.e., the smaller Dx is) , the less accurately you know the momentum (i.e., the larger Dp is); and vice versa.
- 13. It is impossible to know both the position and momentum exactly, i.e., Dx=0 and Dp=0. These uncertainties are inherent in the physical world and have nothing to do with the skill of the observer. Because h is so small, these uncertainties are not observable in normal everyday situations.
- 14. A pitcher throws a 0.1-kg baseball at 40 m/s So momentum is 0.1 x 40 = 4 kg m/s Suppose the momentum is measured to an accuracy of 1 percent , i.e., Dp = 0.01 p = 4 x 10-2 kg m/s
- 15. The uncertainty in position is then No wonder one does not observe the effects of the uncertainty principle in everyday life!
- 16. Same situation, but baseball replaced by an electron which has mass 9.11 x 10-31 kg So momentum = 3.6 x 10-29 kg m/s and its uncertainty = 3.6 x 10-31 kg m/s The uncertainty in position is then
- 17. The more accurately we know the energy of a body, the less accurately we know how long it possessed that energy The energy can be known with perfect precision (DE = 0), only if the measurement is made over an infinite period of time (Dt = ∞)