BOMBS AT BIKINI 



for example, how the intensity of ultraviolet light 

 would compare with the intensity of visible light. Their 

 wonderings led to the preparation of a number of dif- 

 ferent instruments, each designed to answer a specific 

 question. Several broad spectral bands, for example, 

 were to be compared by means of photocells or electric 

 eyes. Each of these electric eyes was deliberately made 

 color-blind to all but a single color — by the use of 

 ''rose-tinted glasses," or glasses of any other color de- 

 sired. Thus each photocell was made ready to report 

 the results in its own spectral zone. For more precise 

 discrimination between different parts of the spectrum, 

 spectrographs were used. These employed small prisms 

 and gratings to separate more cleanly the different 

 wavelengths ; results were recorded on strips of photo- 

 graphic film. 



High-speed techniques also were brought in. Com- 

 mander Ballard knew that tremendous changes would 

 occur in the emission of optical radiation during the 

 first few instants after the detonation. The changes 

 Avould occur hundreds of times too fast for the human 

 eye to notice — even if the eye were not momentarily 

 blinded. To catch these rapid changes, photocells were 

 used. Their responses, free from any appreciable delay, 

 were to be translated by means of cathode ray oscillo- 

 graphs into the usual end-products dear to the heart of 

 scientists : accurate and permanent charts. 



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