The following figure shows a group
of parallel light rays incident on and a group of light rays reflected from a
concave mirror. In which group do all the light
rays pass through point 𝑃? (A) The incident light rays
only. (B) The reflected light rays
only. (C) Both the incident light rays
and the reflected light rays. (D) Neither group of rays.
We want to know whether the
incident light rays, the reflected light rays, or none, or both groups of light rays
pass through this point, 𝑃. We see that of the three incident
rays, red, green, and blue, only the ray depicted by the green line passes through
point 𝑃. This means that option (A) and
option (C) are incorrect.
The green incident ray travels
along the optical axis of the concave mirror. Therefore, the green reflected ray
will be reflected back along its incoming path and will pass through point 𝑃. For the red and blue incident rays,
they hit these points on the concave mirror, and we see that the reflected rays pass
through point 𝑃. So, all three reflected rays pass
through point 𝑃, and we’ve already seen that not all three incident rays do.
Therefore, the answer must be
option (B). The group in which all the light
rays pass through point 𝑃 is the reflected light rays only.