Young’s Double Slit Contents: Interference Diffraction Young’s Double Slit Angle Distance Single slit Rayleigh Criterion

Interference TOC When the difference in distance ( L 1 - L 2 ) is an integer number of wavelengths (0, 1, 2, 3…) = Constructive remainder of a half ( 1 / 2, 1 1 / 2, 2 1 / 2, …) = Destructive L1L1 L2L2 Sources

Young’s Double Slit Experiment TOC Monochromatic, coherent light Light spreads out from slits Screen has sum of two sources Interference pattern on screen Demo

TOC d = slit separation Central Maxima Next Maxima d L1L1 L2L2 L 2 – L 1 = d sin  Young’s Double Slit Experiment

TOC d = slit separation d sin  = n (n = 0, 1, 2…) - constructive d sin  = (n + 1 / 2 ) - destructive Central Maxima Next Maxima d L1L1 L2L2 L 2 - L 2 = d sin   Young’s Double Slit Experiment

Young’s Double Slit - Angle 11 | 2 | 3 | 4234 TOC

d sin  = n d = 3.00 x m, n = 1,  = 6.00 o 314 nm W Two slits are 3.00 x m apart. What is the wavelength of the incident light if the bright fringes are separated by 6.00 o ?

d sin  = n d = 9.00 x m, n = 3, = 565 x m 10.9 o W Two slits are 9.00 x m apart. If 565 nm light is incident, what angle separates the central maxima, and the third fringe out?

TOC Similar triangles - set up proportion s = D d Central Maxima Next Maxima d L1L1 Young’s Double Slit Experiment  D s

Young’s Double Slit Distance 11 | 2 | 3 | 4234 TOC

d = 2.5 x m, D = 5.0 m, = 520 x m.10 m W 520 nm light hits two slits separated by 2.5 x m. What distance separates the bright fringes on the screen that is 5.0 m distant? s = D d

d = 2.50 x m, D = 5.00 m, d =.0570 m 285 nm W Light hits two slits separated by 2.50 x m. If 5.70 cm separates the bright fringes on the screen that is 5.00 m distant, what is the wavelength of light being used? s = D d

A single slit can make an interference pattern too

Rayleigh Criterion  = 1.22 b  = Angle of resolution (Rad) = Wavelength (m) b = Diameter of circular opening (m) (Telescope aperture) the bigger the aperture, the smaller the angle you can resolve. Central maximum of one is over minimum of the other

Rayleigh Criterion 11 | 22 TOC

 = 1.22 b  = ?, = 550 x m, b = 2.54 m  = E x radians W What is the angular resolution of the 100 inch (2.54 m) diameter telescope on the top of Mt Wilson? (use 550 nm as the wavelength) (uh 550 nm = 550 x m)

 = 1.22 b  = 6.00 x 10 -7, = 550 x m, b = ? b = 1.12 m 1.1 m W What diameter telescope do you need to resolve two stars that are separated by 1.8 x m, but are 3.0 × m from us? (use 550 nm as the wavelength) (AU, 32 LY) hint  = s/r = (1.8 x m)/(3.0 × m)