Compton measured the dependence of scattered x-ray intensity on wavelength at three different scattering angles of 45 o 90 o ,and 135 o The intensity was determined by a movable ionization chamber that generated a current proportional to the x-ray intensity. A graphite target was bombarded with monochromatic x-rays and the wavelength of the scattered radiation was measured with a rotating crystal spectrometer. Compton's experiment convinced physicists that light can behave as a stream of particles whose energy is proportional to the frequency.Ī schematic diagram of the apparatus used by Compton is shown in the Figure below. Light must behave as if it consists of particles in order to explain the low-intensity Compton scattering. Thomson scattering, the classical theory of an electromagnetic wave scattered by charged particles, cannot explain low intensity shift in wavelength (Classically, light of sufficient intensity for the electric field to accelerate a charged particle to a relativistic speed will cause radiation-pressure recoil and an associated Doppler shift of the scattered light, but the effect would become arbitrarily small at sufficiently low light intensities regardless of wavelength.). The effect was first demonstrated in 1923 by Arthur Holly Compton (for which he received a 1927 Nobel Prize).The effect is important because it demonstrates that light cannot be explained purely as a wave phenomenon. The scattered radiation experiences a wavelength shift that cannot be explained in terms of classical wave theory, thus lending support to Einstein's photon theory. Hence this wavelength is called Compton wavelength and the shift in wavelength is called Compton shift.The Compton effect (also called Compton scattering) is the result of a high-energy photon colliding with a target, which releases loosely bound electrons from the outer shell of the atom or molecule. The shift in wavelength or difference in wavelength ∆λ of the two scattered beams is found to increase with respect to the increase in the scattering angle.Īt θ = 90 0, the ∆ is found to be 0.0236 0.02424, which has good agreement with the theoretical results. here the peak A is found to be of same wavelength as that of the incident wavelength and the peak ‘B’ is of greater wavelength than the incident radiation now, when the scattering angle is increased, for one incident radiation peak A of wavelength ‘λ’ we get two scattered peaks ‘A’ and B. In this figure when the scattering angle θ = 0 0, the scattered radiation peak will be the same as that of the incident radiation Peak ‘A’. The experimental results are plotted as shown in the figure. The experiment is repeated for various scattering angles and the scattered wavelengths are measured. The scattered X-rays are received with the help of the Bragg’s spectrometer and the scattered wavelength is measured. These X- rays are made to fall on the scattering element. X-rays of monochromatic wavelength ’λ’ is produced from an X-ray tube and is made to pass through the slits S 1 and S 2. Slits S 1and S 2 helps to focus the X-rays onto the scattering element. A small block of Carbon C (scattering element) is mounted on a circular table as shown in the figure.Ī Bragg’s spectrometer (B s) is allowed to freely swing in an arc about the scattering element to catch the scattered photons. It consists of an X-ray tube fro producing X-rays. This effect is called Compton Effect and the shift in wavelength is called Compton Shift. When a photon of energy hγ collides with a scattering element, the scattered beam has two components, viz., one of the same frequencies or wavelength as that of the incident radiation and the other has lower frequency or higher wavelength compared to incident frequency or wavelength. EXPERIMENTAL VERIFICATION OF COMPTON EFFECT
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