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EXPERIMENT 43. THE PATH OF LIGHT THROUGH PLATE 



GLASS 



Fasten a sheet of paper to a table with thumb tacks and 

 at the center of the sheet, place a piece of plate glass so 

 that it is perpendicular to the paper. With a sharp pen- 

 cil, trace on the paper the outline of the glass. 



On the far side of the glass stick two pins upright at the 

 points A and B, as shown in the diagram. With the eye 

 on a level with the table, 

 look through the glass 

 and move the head from 

 side to side until one pin 

 appears to lie directly be- 

 hind the other. Then 

 stick two more pins into 

 the paper on the near 

 side of the glass, in such 

 a position that all four 

 pins seem to lie in the 



FlG. 41. Refraction through plate glass. 



same straight line. 



Remove the piece of 

 plate glass and the pins, 

 draw AB and CD, and prolong these lines until they meet 

 the outline of the glass at the points E and F. Join E and 

 F with a straight line to show the path of the light as it 

 passed through the glass. 



From your result, state what happens (a) when a ray of 

 light passes from air into a piece of plate glass ; (b) when 

 a ray of light passes from a piece of glass into the air. 

 Does the emergent ray differ in direction from the incident 

 ray ? State the law of refraction. 



