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Illuminate a suspended water drop in a vertical pipe with a laser pointer to observe and analyze the intricate patterns created on a screen. Investigate the effects of reflection, refraction, and diffraction on the brilliant pattern formation.
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Brilliant Pattern • Problem • Suspend a water drop at the lower end of a vertical pipe. Illuminate the drop using a laser pointer and observe the pattern created on a screen. Study and explain the structure of the pattern
Overview • Hypothesis • Assumption of Experiment • Experimental Setup • Devices and Process • Investigations • Experimental Results • Theory • The Physics Behind Brilliant Pattern • Conclusion
Hypothesis • Effects of reflection and refraction • Diffraction Geometrical Optics + Physical Optics d/2 a Physical Optics
10 mw, 532 nm, Radius: 1.45 mm 1 mm Laser Pointer 35 cm Experimental Setup
Observation 42o 51o
Theory • Passing through water drop (0o)
Theory • Traveling backwards (180o)
Experimental Results 0o 42o 51o
Experiment 2: Physical Optics • Distance between water drop and screen 4 m • Water Droplet Radius: 0.9~2 mm • Laser Pointer Diameter: 2.2 mm Wavelength: 532 nm
Experiment 2: Physical Optics Diffraction
Theory Huygens’s Principle Every point on a propagating wavefront serves as the source of spherical secondary wavelets, wavelets, such that the wavefront at some later time is the envelope of these wavelets
Theory • Huygens’s Principle • Every point on a propagating wavefront serves as the source of spherical secondary wavelets, wavelets, such that the wavefront at some later time is the envelope of these wavelets
Theoretical Analysis 0.9 mm Diameter of water drop: 1.2 mm 1.5 mm 2.0 mm
0.9 mm 1.2 mm 1.5 mm 2 mm Theoretical Analysis Diameter of water drop:
1.2 mm 0.9 mm 1.5 mm 2 mm Experimental Results Experimental Results 1.2 mm 0.9 mm 1.5 mm 2 mm
Experimental Results 0.9 mm 2 mm
Conclusion • Geometrical Optics: • At 0o the light passes through the water droplet and is magnified • The light is reflected and refracted by the water droplet; thus, interference is demonstrated • At other degrees because the light beam has attenuated its energy so patterns are unable to be observed • Wave Optics: • Due to Huygens’s principle, light is diffracted, so diffraction bands are observable • As water droplets are enlarged the distance between each band decreases