1. 4.3.5 – 4.3.7 4.4.9 – 4.4.13 A.S. Due Monday, May 18

2. Observations (first officially recorded in the 1600’s!) Observations (first officially recorded in the 1600’s!) Frequency, wavelength and speed of waves remain same after diffraction Frequency, wavelength and speed of waves remain same after diffraction Direction of waves will change—the waves will bend around the edge of barriers Direction of waves will change—the waves will bend around the edge of barriers Effect of diffraction is most obvious when aperture (width of the slit) is approximately equal to the size of the wavelength Effect of diffraction is most obvious when aperture (width of the slit) is approximately equal to the size of the wavelength Amplitude of diffracted wave is less than incident wave; energy is distributed over a larger area. Amplitude of diffracted wave is less than incident wave; energy is distributed over a larger area.

3. On a mechanical wavefront, imagine each point to be an individual point source (that creates a circular wavefront) An infinite number of point sources will add together (constructive interference) and form a straight wavefront An infinite number of point sources will add together (constructive interference) and form a straight wavefront As the wavefront passes through an opening (aperture), the point sources at the edges no longer have a neighboring wave with which to interfere, so the circular wavefront is visible, making the wave “bend” around the barrier. As the wavefront passes through an opening (aperture), the point sources at the edges no longer have a neighboring wave with which to interfere, so the circular wavefront is visible, making the wave “bend” around the barrier.

4. When 2 or more waves are in the same place at the same time, the amplitudes at that hoff position will add together to form a single wave Constructive interference: The result of two positive amplitudes adding together (or two negative amplitudes) to form a single wave that has a larger amplitude than either of the two individual waves. Destructive interference: The result of a positive amplitude and a negative amplitude adding together to form a single wave with a smaller overall amplitude. Total Destructive Interference: with the two amplitudes are equal, but opposite—the overall amplitude will be zero, and the medium will appear to not be oscillating

6. Even through a single slit, Light shows patterns that mimic mechanical waves through 2 slits: Central maximum: The brightest section of the light’s interference pattern, directly across from the opening (slit) Bright fringes (maxima): areas where constructive interference occurs Dark fringes (minima): areas where total destructive interference occur

7. Basic Trigonometry, and the fact that light diffracts around both edges of the slit Basic Trigonometry, and the fact that light diffracts around both edges of the slit Path difference: the difference in the distance from one edge of the slit to a point on the screen and the distance from the other edge of the slit to that same point Path difference: the difference in the distance from one edge of the slit to a point on the screen and the distance from the other edge of the slit to that same point

8. In summary: In summary: If the path difference is equal to an integral multiple of the wavelength of light, a maxima will occur (n ) (imagine two crests meeting) If the path difference is equal to an integral multiple of the wavelength of light, a maxima will occur (n ) (imagine two crests meeting) If the path difference is equal to ((n+1/2) ), then a minima will occur. (imagine a crest meeting a trough) If the path difference is equal to ((n+1/2) ), then a minima will occur. (imagine a crest meeting a trough) Fringe order: (Order of the fringe)—is the “n” value Fringe order: (Order of the fringe)—is the “n” value