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CHAPTER III
COLOURS IN STILL WATER
Fig. 20. Refraction of a Fig. 21. Refraction of a
ray of light on entering ray of light on emerging from
water. water.
as distinguished from that due to surface reflexion,
we must trace the passage of light from air into water,
and wice versd, from water into air.
Suppose a beam of light AO (Fig. 20) to strike
the surface of still water at O. A portion of the
light will then be reflected “ regularly " (as explained
in Chapter I) along OB and the remainder will
enter the water. This second portion will not con¬
tinue its course in a straight line to a, but will be