Which wave has the lowest intensity? A) E0 B) E0 C) E0/2 D)  It depends on the color of the light E)  I need more information to answer Razor’s edge Double slit pattern Interference patterns from light Razor’s corner Two Slit Interference Screen Center point is bright point 1 Two Slit Interference Screen Wave Source 1 d Wave Source 2 𝜃 𝜃 “path length difference”=dsin⁠𝜃 => MAXIMA (bright spots) =mλ = (m+1/2) λ => MINIMA ©University of Colorado, Boulder (2008) 2 d 𝜃 “path length difference” = dsin⁠𝜃 = m λ => MAXIMA (bright spots) ©University of Colorado, Boulder (2008) A double slit exp’t is changed so that the pattern covers a smaller portion on the screen. What could account for the smaller pattern? A) Screen was moved further from the slits. B) λ of the laser light was decreased C) The slit spacing was reduced. D) The laser was moved closer to the slits E) More than one of these. Which one is the CD and which is the DVD? A) The Left one is the DVD and Right one is CD B) The Right one is the DVD and the Left one is the CD C) There is no way to tell ©University of Colorado, Boulder (2008) 3 Recall, for 2 slits: d sinθ = (integer)* λ => MAXIMA (bright spots) Red and green light are both shining on the same double slit. Which pattern has the bright spots spread farther apart? A) Green light bright spots are farther apart B) Red light bright spots are farther apart. C) All bright spots are equally far apart White light (rather than a monochromatic laser) illuminates a diffraction grating. What does the pattern on the most screen look like? A) Bright white dots at various angles (given by the usual formula) B) “Rainbows” at various angles C) One central maximum is a white dot, surrounded by rainbows D) Something else. ©University of Colorado, Boulder (2008) Laser light, wavelength λ, illuminates a mask with 2 slits. You see exactly 3 bright spots (a central one, +1 on each side). What can you conclude about the slit spacing d? A)  d>λ and I (and/or my group) are confident B) d>λ (not so confident!) C)  d<λ and I (and/or my group) are confident D)  d<λ (not so confident!) 4 Small angle approx •  𝑚𝜆/𝑑 =sin⁠𝜃 •  sin⁠𝜃 ≈𝜃≈tan⁠𝜃 = 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑠𝑝𝑎𝑐𝑖𝑛𝑔/ 𝑠𝑐𝑟𝑒𝑒𝑛 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 (Only works if the angle is in radians!!) ©University of Colorado, Boulder (2008) Single slit diffraction Single slit diffractionv θ= mλ D Minima of dark spots in single slit pattern 5 Diffraction limited images of two stars from a 2.6 m telescope ©University of Colorado, Boulder (2008) The Hubble Space Telescope has a "lens" (actually a mirror) of diameter of a couple of meter. For which color light will the HST have the BEST resolution? A) Blue B) Yellow C) Red D) Resolution is independent of color. Track separation on a reflective grating is 5 µm (5 E-6 m). Is it possible to separate visible light (λ=400-700 nm, 1 nm = 1E-9 m) with it? A)  B)  C)  D)  E)  Yes, of course ! Yes, I guess. No, of course not ! No, I guess. I do not know how to answer this question. ©University of Colorado, Boulder (2008) 6 What is the spacing of our diffraction gratings if the screen is 2 𝑚 away and the dot spacing is Δx=54 cm for a green laser with 𝜆=532 𝑛𝑚 A)  ~530 nm B)  ~150nm C)  2 𝜇m D)  5 𝜇m E)  More information is needed ©University of Colorado, Boulder (2008) ©University of Colorado, Boulder (2008) 7