CH. XIV. LIGHT AND ENERGY LOSSES IN PROJECTION 605 



of water of different thickness. The lower line represents the 

 energy transmission. About 10% of the light (and energy) is lost 

 by non-selective reflection. If one wished to know the amount of 

 energy transmitted to get the same light transmission, it is neces- 

 sary to add 10% to the above values. The upper line represents 

 the transmitted energy after the correction for reflection has been 

 made. These curves show that after the first four or five centi- 

 meters of water, increased thickness does not reduce the energy 

 very much. A 6 cm. layer of water transmits 22.5%, a 10 cm. 

 layer transmits 20%, the difference absorbed in the last 4 cm. being 

 but 2.5% of the incident energy. 



The water-cell, by absorbing a great deal of the energy, reduces 

 the heating effect of the light on the specimen. This energy 



246 8 1.0 \i 1.4 



Thichness Centimeters 



Z 4 6 8 1.0 II 

 Thichness Centimeters 



FIG. 340-341. PERCENTAGE OF ENERGY FROM T THE'CRATER OF THE RIGHT- 

 ANGLE ARC TRANSMITTED BY LAYERS OF,WATER OF DIFFERENT THICKNESS. 



The lower curve shows the actual energy[ transmission in each case, and 

 the upper curve shows the actual energy transmission corrected for reflection. 



