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DON’T REGRET MISSING OUT ON VALLEYFAIR. Reflection. Convex / Concave Mirrors Diffuse Reflections The Reflection of Sound. Convex Mirrors. Mirrors that bulge out. Produce a virtual image that is smaller and closer to the mirror than the object is.
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Reflection Convex / Concave Mirrors Diffuse Reflections The Reflection of Sound
Convex Mirrors • Mirrors that bulge out. Produce a virtual image that is smaller and closer to the mirror than the object is. • http://www.edumedia-sciences.com/a309_l2-convex-mirror.html
Concave Mirrors Now I’m large enough to destroy the world! Mwa ha ha! • Mirrors that “cave” in. Produce a virtual image that is larger and farther away from the mirror than the object is (when the object is close to the mirror). http://www.edumedia-sciences.com/a308_l2-concave-mirror.html
Diffuse Reflections • The reflection of waves in many directions from a rough surface. • Each ray obeys the law of reflection, but on a rough surface, there are many different angles.
Is this a smooth surface? For light, this is a rough surface. But for long-wavelength radio waves, this is a polished surface. It is like a mirror to radio waves. The longer the wavelength, the more polished a rough surface looks.
Reflection of Sound Sound is a wave, so it can be reflected.
Sound reflects better off of rigid and smooth surfaces. Sound energy that is not reflected is absorbed or transmitted. • Reverberation: the persistence of sound, as in an echo, due to multiple reflections.
The Concert Hall • Too much reverberation = garbled sound • Too much absorption = quieter, duller sound. • We want a balance between reverberation and absorption. • Is it better to have smooth walls in a concert hall, or to have rough walls?
The Concert Hall • Want both! • Grooves in the wall make sure that the sound a person hears is from many parts of the wall. • Reflective surfaces are placed behind the stage to direct sound out to the audience.