Question Video: Describing the Position of a Real Image | Nagwa Question Video: Describing the Position of a Real Image | Nagwa

# Question Video: Describing the Position of a Real Image Science

The figure shows two light rays from the same point on an object that are incident on a concave mirror. The object is between the center of curvature of the mirror and the focal point of the mirror. A real image is produced. Which of the following is the location of the image? [A] Between the focal point and the center of curvature of the mirror [B] At the center of curvature of the mirror [C] At the focal point of the mirror [D] At the surface of the mirror [E] at a distance from the surface of the mirror greater than the distance to the center of curvature of the mirror as measured parallel to its optical axis

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### Video Transcript

The following figure shows two light rays from the same point on an object that are incident on a concave mirror. The object is between the center of curvature of the mirror and the focal point of the mirror. A real image is produced. Which of the following is the location of the image? (A) Between the focal point and the center of curvature of the mirror. (B) At the center of curvature of the mirror. (C) At the focal point of the mirror. (D) At the surface of the mirror. Or (E) at a distance from the surface of the mirror greater than the distance to the center of curvature of the mirror as measured parallel to its optical axis.

An image is the point where reflected rays with the same origin intersect. Here, we have two reflected rays, which have the same origin. So, we must look at the reflected rays and see where they intersect. None of the reflected rays intersect in the region between the center of curvature and the focal point. So, option (A) can be eliminated.

The center of curvature contains no rays passing through it, neither incident nor reflected. So, option (B) can be eliminated as well.

We see that only one reflected ray, the red one, passes through the focal point. The blue incident ray passes through it. However, its reflected ray is what helps makes up the image, but this does not pass through the focal point. Therefore, option (C) can be eliminated.

It is true that there are rays at the surface of the mirror. However, the reflected rays do not intersect at the surface of the mirror. So, option (D) can be ruled out.

All light rays from the origin that are reflected by the mirror will meet at the point where the real image is produced. We can see that the two reflected rays meet at this point that we will call point 𝑃, and this is where the image is produced. If we look at the distance between the surface of the mirror and its center of curvature along the optical axis of the mirror and compare it to the distance from the surface of the mirror to point 𝑃 along the optical axis of the mirror, we can see that point 𝑃 is further from the surface of the mirror than the distance from the surface of the mirror to its center of curvature.

Therefore, the correct answer is option (E). The location of the image is at a distance from the surface of the mirror greater than the distance to the center of curvature of the mirror as measured parallel to its optical axis.