8B - 16_Interference_11.ppt

# 8B - 16_Interference_11.ppt - General Properties 0f Waves...

This preview shows pages 1–11. Sign up to view the full content.

General Properties 0f Waves If it is a wave, it usually has the following physical properties. What we learn about EM waves applies to sound waves and waves of elementary particles: Wavelength Frequency Energy Momentum Pressure Polarization Reflection Refraction Diffraction Interference Localization by superposition of various wavelengths Total Internal Reflection - Frustrated (Tunnel) Standing waves (modes of vibration)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Huygens' Principle All points on a wavefront serve as point sources of secondary wavelets. After a time t , the new position of the wavefront will be that of a surface tangent to these secondary wavelets. Physically, the driven oscillators reemit waves of same frequency; speed of wave and wavelength may change.
Phase of Wave A sine wave can be thought of as sweeping through 360º. Amplitude of wave is the x-projection of a rotating unit vector. The phase is the angle that has been swept. ! Phase difference between 2 waves = angular difference between 2 comparable points. 90º in this example.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Phase differences give Interference Phase difference can be stated in A) Angle (degrees, radians = 2 π {path diff. / λ }) B) Fraction of a wavelength Superpose 2 waves Result: 0º, 0 rad. in phase 180º, π λ /2 120º, 2 π /3 λ /3
Interference - the math Add two sinusoids of same frequency and amplitude, in same direction,but differing phases :

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Resultant Waves http://www.kettering.edu/~drussell/Demos/superpositi on/superposition.html
Criteria for Interference Same frequency Phase difference - due to path, material, or reflection difference Stable phase (coherence) Use split light or laser Same polarization …. Then can add 2 or more waves

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Essence of waves: 1 + 1 = ? http://www.teachspin.com/instruments/two_slit/experiments.shtml Two one-slit patterns superpose to give a series of narrow peaks. The envelope of the two-slit pattern is the one-slit pattern.
Phase Difference by Path - Michelson's Interferometer Michelson's interferometer, showing the path of light originating at point P of an extended source S. Mirror M splits the light into two beams, which reflect from mirrors M 1 and M 2 back to M and then to telescope T . In the telescope an observer sees a pattern of interference fringes. Michelson and Morley were not able to detect a change in speed of light due to motion of the Earth. This is explained by Special Relativity which says c = constant.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Demo - Michelson Interferometer Microwave interference by multiple reflection - Michelson’s interferometer Changing the path length in one arm produces a series of maxima and minima at the detector.
This is the end of the preview. Sign up to access the rest of the document.

## 8B - 16_Interference_11.ppt - General Properties 0f Waves...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online