Handbook of High Speed Photography - IET Labs, Inc.
Handbook of High Speed Photography - IET Labs, Inc.
Handbook of High Speed Photography - IET Labs, Inc.
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Figure 4-8. Shock-wave photography with a Scotchlite screen.<br />
(Photograph courtesy <strong>of</strong> Dr. Harold E. Edgerton, M.I.T.)<br />
This shadow photograph <strong>of</strong> a .30-calibre bullet being fired from a Springfield<br />
rifle clearly outlines the spherical sound wave emanating from the gun's muzzle.<br />
In the original photograph, the conical shock layer <strong>of</strong> compressed air extending<br />
back from the bullet's nose can be seen; similar shock waves produce earsplitting<br />
sonic booms when jet planes break the sound barrier.<br />
A 4-foot reflective screen <strong>of</strong> Signal Silver Scotchlite was located 10 feel from<br />
the camera. The rifle was<br />
screen 5 feet from the camera. A<br />
135-mm lens was used at<br />
f/4.7 with Polaroid Type<br />
52 positive film (ASA<br />
200). A microphone trig<br />
gered the high-intensity<br />
Strobotac flash.<br />
Strobotac used as a point light<br />
source. The spark gap must be<br />
oriented parallel to the camerasubject<br />
axis and as close beside<br />
the camera lens as possible.<br />
36
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