BIOLOGICAL EFFECTS OF RADIATIONS 



699 



electrons. Such radiations are heat, infrared, visible, and ultraviolet. 

 Heat and infrared radiation penetrate slowly and the quanta are 

 comparatively small. The quanta of visible light are larger and 

 the wave lengths are shorter. Such radiations are easily absorbed 

 by even light elements except that some light is transmitted by 



k 



I 



"Wavelength 



Anpstrora 



1. 



6 



7 



4' 



15 



15 



11 



-4- 

 10 J 



10^ 



1 



10 - 



10 -- 



JO 



lo'S 



10 -\ 



other 

 units 



10 cm. 



- Cosmic 



10 ctn.-""* 



•1 MilU- 

 tnxcron 



10-^ 



_ Ultrdviolet 



10 - -1 Micron " 



.IMUl'i- . 

 meter 



■1 Centi- 

 meter 



10 - -1 Meter - 



'iKUo- 

 ■meter 



Types 

 of 



radiation 



Gamtna 

 rays 



Roerxtgerv 

 or 

 X-VAys 



Visible 



Infra- 

 red 



Short electric 



Hertzian 



Wireless 



Therapeutic 

 effects 



No 



.1 





Anti-7dctiitic 



Photic 



Elevates 

 "tempera.- 



Artiflcldl 

 fevers and 

 diatherraic 

 effects 



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c: 

 s 







CO 



Pig. 369. — Chart of wave radiations. Visible light contains different radia- 

 tions which appear as colors to the human eye. The long wave length radiation is 

 the red, and in order of decreasing wave length the others are orange, yellow, 

 green, blue, and violet. Visible light covers a range of one octave, as the wave 

 length of the red radiation is twice that of the violet. The range of wave length 

 for the infrared is much greater as it can be seen that the wave length doubles 

 itself thirteen times. (From Sheard, Lifegiving Light, published by Williams & 

 Wilkins Company.) 



glass. Ultraviolet radiations have wave lengths shorter than that 

 of visible light and penetrate opaque substances to a greater degree. 

 Ultraviolet is also more chemically active since the contained quanta 



