Newall, H. F · London : Society for Promoting Christian Knowledge · leaf 25
all directions,and the action of the perforated screen is to cut offall rays that fall upon it except those which passthrough the hole. We shall frequently use the conception of rays,but it must be remembered that a juster view ofthe matter is to think of each point of the candle- 18 THE… … Fig. 3. dealt with in this primer are concerned, to be con-sidered as being always at right angles to the frontsof the waves. When waves spreading from everypoint in a candle-flame (Fig. 4) reach a screen in
Spectroscope · Spectrum analysis
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