The Mystery of Light

author: Walter H. G. Lewin, Center for Future Civic Media, Massachusetts Institute of Technology, MIT
published: Aug. 24, 2011,   recorded: July 2004,   views: 10033

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An alternate title for this talk might be “Walter’s World of Waves.” First, Lewin methodically explores how water and sound move in traveling waves. With a pan of water and a tuning fork, Lewin demonstrates concepts of oscillation, amplitude and velocity. He deploys equations for determining wavelengths and measuring frequency. By tapping water, he illustrates constructive interference, where “waves support each other” and achieve maximum amplitude. Then Lewin synchronizes two water waves so that the peak of one wave arrives precisely at the valley of the other, and “the two waves annihilate each other.” The same principles apply to sound. Lewin broadcasts tones from loudspeakers, and gets heads bobbing as listeners try to detect if two sound waves are capable of destroying each other to produce silence. If experiments like these show how sound and water move in waves, can he similarly demonstrate that light exists as waves? He replicates with a red laser an experiment from 1801 that yielded such proof, “that light plus light can give darkness.” When he aims his bright light at two openings, Lewin gets areas of darkness and areas of light, evidence of both destructive and constructive interference. But while he offers definitive proof that light travels in waves, Lewin concludes that it also exists as particles, “a great mystery of physics that causes me and others sleepless nights.”

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Reviews and comments:

Comment1 Telc Goethe, August 29, 2022 at 1:58 p.m.:

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Comment2 Joe Mama, September 2, 2022 at 3:59 p.m.:

When they collide with an opaque object, the light is blocked, creating a shadow. A shadow is just the lack of light. The surface (such as the ground or a wall) on the other side of an item will get less light if light cannot pass through that object. Click here to find out more about I Love Hue.

Comment3 Deez Nuts, September 2, 2022 at 4:01 p.m.:

The Form Shadow Core is the darkest region of the shadow, while the remaining portions of the Form Shadow are composed of dark tones that fade into any reflected light that may be present. Reflected light is the light that an item receives from its surroundings or from the surface it is resting on. Check out this Guide:

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