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· Ar ag O 5 p Ot Ver if iCati On •.· _~ ~~-c· < c:~ . . ~J,,, MIDN 4/C Joo-Won Lee, Peter Sinkovitz, Elizabeth Troy, ~hristopher Wellins (~~ ~~/. .;,, ,} Associate Professor Cody J. Brownell, Mechanical Engineering Department ' • - • - Professor Svetlana Avramov-Zamurovic, Weapons & Systems Department . . ,' · , : . •.

Abstract Methods Conclusion • Materials gathered: Levitator, Thorlabs Model HNL0S0L Laser, laser camera, camera filter, pipet, In the shadow of an object, there is a small The Arago spot is present in all of the liquids. The white liquid for Arago Spot, computer (BeamGauge & MATLAB) and chocolate milk were used as opaque substances. bright spot created by diffraction called the • Water, White Milk (Opaque 1), Chocolate Milk (Opaque 2) The white milk had a very smooth surface compared to Arago spot. Using a 10 mW laser, the Arago • Align the laser, levitator, and the camera to the correct height and angle the chocolate milk, likely due to a lower sugar content, effect was studied on different types of liquid • Using a 10 µL pipette, place a liquid drop in the levitator which caused the light intensity at the Arago spot to be spheres. The goal of this experiment was to • Take a picture of the beam using BeamGauge software brighter. The Fresnel diffraction was also affected by develop a deeper understanding of the • Analyze the picture in MATLAB to make the Arago spot graph the distance between the laser and the drop, the size of influence of object opacity on the Arago the drop, and the distance from the camera to the effect. Graphs drop. The Arago spot increa ses proportionally to Results increases in radius and distance from the camera to the Background droplet. The brightness is determined by the substance !l We observed bright spots in the middle that the laser travels through. In order to achieve more Laser systems have become prominent in naval • of the first grayscale photo taken when precise results, a more advanced levitator would be warfare with regards to communication and I the laser was shined through the first required to levitate solid objects to gauge more opaque sensors; understanding the effect that the opaque droplet. Although the image substances. It would also be beneficial to attain a operating environment has on beams is crucial to does not portray a perfect circular precise measurement of the liquid drops, in o rder to accurate and effective deployment. The "Arago observe accurate trends with varying volumes. J shape, the brightness of the laser is Spot" phenomenon, a bright point that appears at ! the center of a circular object's shadow due to greatest at the center of the oval Fresnel diffraction, was discovered by Simeon J object. The second opaque test References Poisson when he placed a circular object in front of ) further corroborates these findings, Born, Max; Wolf, Emil (1999), Principles of optics (7th, a light . These findings had tremendous impact showing a more defined and sharper expanded ed.), Cambridge University Press, ISBN 0-521- upo n t he physics community, confirming the wave­ I bright spot in the center of the shadow. 64222-1 Hecht, Eugene. "Brown University." Search Results I like nat ure of light propagation. Our experiment I The tendency of the laser to trail to the Department of Physics. Accessed April 17, 2017. attem pted to refine these findings by levitating ! bottom right is due to large laser beam https://www.brown.edu/academics/physics/search/google liquid droplets, shooting lasers through them, and ?cx=001311030293454891064%3Alwlrsw9qt3o&cof-FORI j imperfectly aligned. D%3All&query=Poisson%27s%2Bspot&sa.x-ll&sa.y=19& analyzing the shadow cast by the substance. J form id=brown google cse searchbox form. Ohanian, Hans (1989), Physics (2nd ed .), W.W. Norton, p. 9B4, ISBN 0-393-95786-1 School of Physics Sydney, Austral ia. "Poisson-Arago dot." Poisson-Arago dot: Ph ysclips - Light. Accessed April 17, 2017. Huygens-Fresnel Principle http://www.animations.physics.unsw.edu.au/jw/light/Pois son-Arago-dot.html#l. Ae•kro eikr1 U(Pi) = --1-- K(x)dS, ro s r1 Acknowledgemen r. distance of the point P, on the screen from the optical axis Mechanical Engineering Department d: diameter of circular object • Weapons & Systems Engineering /1 : wavelength Department b: distance between circular object and screen • Chemistry Department Multimedia Support Center