Solutions 309
/al< R 2. For a ray propagating at a distance h 2 ,
the distance x 2 = 3.125 cm. Finally, we obtain
= X2 - X1 CY. 0.6 cm (^) 0 (1)
Fig. 244
4.20. Let us consider a certain luminous point A
of the filament and an arbitrary ray AB emerging
from it. We draw a plane through the ray and the
filament. It follows from geometrical considerations