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compare a ray of light not to a single strip of card, but to a bundle of such strips with their edges in all directions, not a tight bundle, but a loose bundle in which one strip does not interfere with another. Now what would happen if we tried to bend the whole bundle in any particular direction? Some of them would have their edges turned in that direction and would refuse to bend at all;

Fig. 78.

others would have their flat sides and would bend easily; and we may say that after bending we should have only strips with their flat sides more or less in the right direction. So it is with a ray of light which is bent by being reflected from a solid particle. If there are solid particles in the corona, then we see them because the sunlight which shines on them is bent