. The Ontario high school physics. hown in the Fia. 237.—A simple form of man- •^^ • ,i rr j. t ometricfiame capsule. AA\^ dotted line. Will lucrcase the eiiect. in a cork hollowed out, M is the . • e. thin membrane. placc of the rotating mirror a piece oi mirror 6 by 8 inches square, held in the hand almost verticaland given a gentle oscillatory motion will give good results. 229. Sympathetic Vibrations. Let us place two tuning-forks, have the same vibration numbers, with the openends of their resonance boxesfacing each other and a shortdistance apart (Fig. 238). Nowvibrate one of the
. The Ontario high school physics. hown in the Fia. 237.—A simple form of man- •^^ • ,i rr j. t ometricfiame capsule. AA\^ dotted line. Will lucrcase the eiiect. in a cork hollowed out, M is the . • e. thin membrane. placc of the rotating mirror a piece oi mirror 6 by 8 inches square, held in the hand almost verticaland given a gentle oscillatory motion will give good results. 229. Sympathetic Vibrations. Let us place two tuning-forks, have the same vibration numbers, with the openends of their resonance boxesfacing each other and a shortdistance apart (Fig. 238). Nowvibrate one of them vigorouslyby means of a bow or by strikingwith a soft mallet (a rubberstopper on a handle), and afterit has been sounding for a few seconflq brino- it to rest bv Fia. 238.—Two tunins-forks arranged toSeCOnUb Uling lU W xebU uy show sympathetic vibrations. When one placing the hand upon it. The is vibrated the other responds. sound will still be heard, but on examination it will befound to proceed from the other ILLUSTHATIONS OF SYMrATHETIC VIBRATIONS—BEATS 203 This ilhistrates tlie plienomenon of sympathetic first fork sets up vibrations in tlie resonance box on wliichit is niounted, and tliis produces vibrations in tlie inclosedair column. The waves proceed from it, and on reaching theresonance box of the second fork its air column is put invibration. The vibrations are communicated to the box andthen to the fork, which, having considerable mass, continues itsmotion for some time. A single wave from the first fork would have little effect,but when a long series comes in regular succession each helpson what the one next before it has started. Thus the effectaccumulates until the second fork is given considerable motion,its sound being heard over a large room. For this experiment to succeed the vibration numbers ofthe two forks must be accurately equal. 230. Illustrations of Sympathetic Vibrations. The pen-dulum of a clock has a natural period
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
