---
title: "An object of constant height is positioned on the principal axis of a concave spherical mirror of focal length \\(f\\), at an initial distance \\(d_o > 2f\\) from the mirror. The object moves toward the mirror along the principal axis at a constant speed \\(v_0\\). Which of the following correctly describes the direction of motion of the real image, the speed \\(v_i\\) of the image at the instant the object reaches the center of curvature (\\(d_o = 2f\\)), and the change in image height as the object approaches \\(2f\\)?"
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url: "https://nerd-notes.com/ubq/123255/"
date_modified: "2026-09-28T11:58:02+00:00"
---

# An object of constant height is positioned on the principal axis of a concave spherical mirror of focal length \(f\), at an initial distance \(d_o > 2f\) from the mirror. The object moves toward the mirror along the principal axis at a constant speed \(v_0\). Which of the following correctly describes the direction of motion of the real image, the speed \(v_i\) of the image at the instant the object reaches the center of curvature (\(d_o = 2f\)), and the change in image height as the object approaches \(2f\)?

An object of constant height is positioned on the principal axis of a concave spherical mirror of focal length \(f\), at an initial distance \(d_o > 2f\) from the mirror. The object moves toward the mirror along the principal axis at a constant speed \(v_0\). Which of the following correctly describes the direction of motion of the real image, the speed \(v_i\) of the image at the instant the object reaches the center of curvature (\(d_o = 2f\)), and the change in image height as the object approaches \(2f\)?

![A horizontal line represents the principal axis. On the right, a concave spherical mirror is shown as a thin vertically curved arc facing left. Two tick marks lie on the principal axis to the left of the mirror: the focal point labeled F at distance f from the mirror, and the center of curvature labeled C at distance 2f from the mirror. To the left of C, a vertical upright solid arrow represents the object. Directly above the object arrow, a horizontal arrow points to the right toward the mirror, labeled v_0. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596682-gNI4rz.jpg)

- **A.** The image moves away from the mirror with instantaneous speed \(v_i = v_0\) at \(d_o = 2f\), and the image height increases.
- **B.** The image moves toward the mirror with instantaneous speed \(v_i = v_0\) at \(d_o = 2f\), and the image height decreases.
- **C.** The image moves away from the mirror with instantaneous speed \(v_i = 2v_0\) at \(d_o = 2f\), and the image height increases.
- **D.** The image moves away from the mirror with instantaneous speed \(v_i = \dfrac{1}{2}v_0\) at \(d_o = 2f\), and the image height decreases.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123255/*