Heisenberg uncertainty principle 2.pptx

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1. Presented by- Ajay kant M.Sc. 1 st semester Physics Department 

2. Hesinberg uncertainty principle Werner Karl Heisenberg

3. Classical world vs Quantum world :- Classical world The observer is objective and passive . Physical events happen independently of whether there is an observer or not . This is known as objective reality . Quantum world * The observer is not objective and passive. The act of observation changes the physical system irrevocably . This is known as subjective reality .

4. Introduction :- Uncertainty principle was stated by Werner Karl Heisenberg in 1927. This principle states that the position and momentum of a particle can not be simultaneously measured with arbitrary high precision. There is a minimum for the product of the uncertainties of the two measurements.

5. Heisenberg light and electrons :- * Measuring the position of a very small particle such as an electron requires the use of short wavelength light (high frequency, high momentum) . High frequency light will alter the electron ‘s momentum . Use low frequency ( long wavelength ) light and the position of the electron is not well determined .

6. Heisenberg principle – equation : - The Heisenberg uncertainty has several forms . We denote the uncertainty in momentum and position.

7. Why this happens :- In the world of very small particles, one can’t measure any property of a particle without interacting with it in some way and this interaction changes related property . ## Measuring p and x of electron – so to determine the position accurately it is necessary to use light with a short wavelength . By Planck's law E = hV , a photon with a short wavelength has a large energy . So will give 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.

8. *Qualitatively if an indentical experiment involving an electron is performed many times and in each the position of electron is measured then for same momentum measurement of position will be different each time . If x is average then standard deviation gives

9. Mathematics expression:-

10. Small uncertainty in x . Large uncertainty in x .