© 2012 Pearson Education, Inc. { Chapter 35 Interference (not given– computer problems)

© 2012 Pearson Education, Inc. Wave fronts from a disturbance  Figure 35.1 at the right shows a “snapshot” of sinusoidal waves spreading out in all directions from a source.  Superposition principle: When two or more waves overlap, the resultant displacement at any instant is the sum of the displacements of each of the individual waves.

© 2012 Pearson Education, Inc. Last Time – constructive/destructive interference  Figure 35.2 at the right shows two coherent wave sources.  Constructive interference occurs when the path difference is an integral number of wavelengths.  Destructive interference occurs when the path difference is a half- integral number of wavelengths.

© 2012 Pearson Education, Inc. Two sources S 1 and S 2 oscillating in phase emit sinusoidal waves. Point P is 7.3 wavelengths from source S 1 and 4.3 wavelengths from source S 2. As a result, at point P there is Q35.1 A. constructive interference. B. destructive interference. C. neither constructive nor destructive interference. D. not enough information given to decide

© 2012 Pearson Education, Inc. Two sources S 1 and S 2 oscillating in phase emit sinusoidal waves. Point P is 7.3 wavelengths from source S 1 and 4.3 wavelengths from source S 2. As a result, at point P there is A35.1 A. constructive interference. B. destructive interference. C. neither constructive nor destructive interference. D. not enough information given to decide

© 2012 Pearson Education, Inc. Two sources S 1 and S 2 oscillating in phase emit sinusoidal waves. Point P is 7.3 wavelengths from source S 1 and 4.6 wavelengths from source S 2. As a result, at point P there is Q35.2 A. constructive interference. B. destructive interference. C. neither constructive nor destructive interference. D. not enough information given to decide

© 2012 Pearson Education, Inc. Two sources S 1 and S 2 oscillating in phase emit sinusoidal waves. Point P is 7.3 wavelengths from source S 1 and 4.6 wavelengths from source S 2. As a result, at point P there is A35.2 A. constructive interference. B. destructive interference. C. neither constructive nor destructive interference. D. not enough information given to decide

© 2012 Pearson Education, Inc. Two-source interference of light Figure 35.5 below shows Young’s double-slit experiment with geometric analysis.

© 2012 Pearson Education, Inc. Interference from two slits Follow the text discussion of two-slit interference. Figure 35.6 at the right is a photograph of the interference fringes from a two-slit experiment.

© 2012 Pearson Education, Inc. In Young’s experiment, coherent light passing through two slits (S 1 and S 2 ) produces a pattern of dark and bright areas on a distant screen. If the wavelength of the light is increased, how does the pattern change? Q35.3 A. The bright areas move closer together. B. The bright areas move farther apart. C. The spacing between bright areas remains the same, but the color changes. D. any of the above, depending on circumstances E. none of the above

© 2012 Pearson Education, Inc. In Young’s experiment, coherent light passing through two slits (S 1 and S 2 ) produces a pattern of dark and bright areas on a distant screen. If the wavelength of the light is increased, how does the pattern change? A35.3 A. The bright areas move closer together. B. The bright areas move farther apart. C. The spacing between bright areas remains the same, but the color changes. D. any of the above, depending on circumstances E. none of the above

© 2012 Pearson Education, Inc. In Young’s experiment, coherent light passing through two slits (S 1 and S 2 ) produces a pattern of dark and bright areas on a distant screen. What is the difference between the distance from S 1 to the m = +3 bright area and the distance from S 2 to the m = +3 bright area? Q35.4 A. three wavelengths B. three half-wavelengths C. three quarter-wavelengths D. not enough information given to decide

© 2012 Pearson Education, Inc. In Young’s experiment, coherent light passing through two slits (S 1 and S 2 ) produces a pattern of dark and bright areas on a distant screen. What is the difference between the distance from S 1 to the m = +3 bright area and the distance from S 2 to the m = +3 bright area? A35.4 A. three wavelengths B. three half-wavelengths C. three quarter-wavelengths D. not enough information given to decide