Johnson's natural philosophy and key to philosophical charts : illustrated with 500 cuts; being reduced photographic copies of all the diagrams contained in the author's philosophical series of indestructible school charts ; for the use of schools and families (1878)
ci ofan ellipse.—If the figure be an ellipse and a wave emanate from F,Pj(j 5 one of the foci, all the rays will converge, so as to fall simultane-ously, after reflection, at theother focus L, as shown by thelines. This is because the an-gles of incidence are equal tothose of reflection, from…
Physics · Astronomy
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