1. MS. Ankita P. Angre Dept. of Physics
Dnynasadhana college, Thane
Class-F. Y. B. Sc.
Subjet-Physics
Paper-II
SEMESTER II
Topic: Compton Effect
MS. Ankita P. Angre
Dept. of Physics

2. Compton Effect Einstein said light consists of quanta of energy (1905)
He did NOT treat momentum until later (1906)
He said momentum = E/c = hf/c
Debye and Compton treated photon-particle collisions much later (1923)

3. X-Rays Discovered in 1895 by Roentgen
High speed electrons onto a metal target and get a new highly penetrating radiation
Medical X-Rays came within months
EM waves with very short wavelengths (very high frequency)
Wavelengths of about meters, same spacing as atoms in crystals

4. Spectrum of X-Rays Broad continuous spectrum
Characteristic lines from different elements
Bremsstrahlung (braking radiation)
eV=hf=hc/min
min=hc/eV where V is tube voltage
Already evidence of particle nature of
x-rays

5. X-Ray Scatting from Crystals
Atoms in successive planes scatter constructively if path difference is a whole number of wavelengths, n=2dsin n=1,2,3…. d  A C   B

6. Compton Effect Considered X-rays scattering from free electrons
Classically, should get re-radiation at equal or lower frequencies
Classically, re-radiated frequency depends on intensity and exposure time
Experimentally, frequency shift is independent of time and intensity

7. Compton Effect Wavelength shift depends only on scattering angle
Consider a collision between a photon and a free electron
Photon energy is hf and momentum is hf/c
Do a relatavistic calculation

8. Compton Effect
Ee. pe
Photon, E, p  
E’<E,p’

9. Compton Effect

10. Compton Effect
Eliminate  and solve for pe

11. Compton Effect
So, shift only depends on angle and gives a result that agrees with experiment

12. THANK YOU !!!!