Jorun draws a ray from her object through the focal point of a concave mirror. It strikes the mirror. The parallel ray rule says nothing about this ray, because it did not arrive parallel.
The second special beam is the first one run backward. This lesson states the focal point ray rule.
Rule 1 took a parallel ray in and sent it out through the focal point.
The second rule is the first one reversed.
Jorun's ray passed through the focal point of her concave mirror on its way in, so its reflection runs parallel to the principal axis.
On a convex mirror the focal point sits behind the mirror, so an arriving ray can only head toward it. That ray also reflects parallel to the principal axis.
Rules 1 and 2 are each other reversed: parallel in gives through the focal point out, and through the focal point in gives parallel out.
Which rule applies is read off the incoming ray: parallel in, rule 1; through or toward the focal point in, rule 2.
A ray leaves an object, passes through the focal point of a concave mirror, and strikes the mirror low on its surface. Where does its reflection go?
The incoming ray passed through the focal point.
The focal point ray rule sends its reflection out parallel to the principal axis.
The reflected ray runs parallel to the principal axis.
Two rays strike a concave mirror. Ray A arrived parallel to the principal axis; ray B passed through the focal point on its way in. Which reflection is parallel to the axis?
Ray A arrived parallel, so rule 1 sends its reflection through the focal point.
Ray B came through the focal point, so rule 2 sends its reflection out parallel to the principal axis.
Ray B's reflection is the parallel one.
A ray passes through the focal point of a concave mirror on its way to the mirror. Where does the reflected ray go?
Katla says: 'A ray heading toward the virtual focal point of a convex mirror reflects parallel to the principal axis.' Is Katla correct?
Lennart says: 'A ray that passes through the focal point of a concave mirror reflects back through the focal point again.' Is Lennart correct?
Which of the following states the focal point ray rule for curved mirror diagrams?
On Ivor's convex mirror diagram, an arriving ray heads toward the virtual focal point behind the mirror. Which describes its reflection?
On a finished concave mirror diagram, one reflected ray runs parallel to the principal axis. Which incoming ray produced it?