Incident ray X passes parallel to the principal axis of a concave lens. Incident ray Y passes parallel to the principal axis of a convex lens. How do the rays behave differently after passing through each lens?

A concave lens makes parallel rays diverge, so ray X appears to have come from the focal point in front of the lens. A convex lens makes parallel rays converge, so ray Y passes through the focal point on the other side. Therefore, choice B describes the different behaviors.

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