---
title: "Two flat, planar mirrors are joined at a right angle (90^\\(90^\\circ\\)). A ray of monochromatic light traveling in the plane of the page is incident on the horizontal mirror at an angle \\(\\theta\\) relative to the surface normal, where \\(0^\\circ < \\theta < 90^\\circ\\), and subsequently reflects toward the vertical mirror. Which of the following diagrams correctly represents the complete path of the light ray and its reflections off both mirrors?"
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url: "https://nerd-notes.com/ubq/123420/"
date_modified: "2026-09-28T11:58:29+00:00"
---

# Two flat, planar mirrors are joined at a right angle (90^\(90^\circ\)). A ray of monochromatic light traveling in the plane of the page is incident on the horizontal mirror at an angle \(\theta\) relative to the surface normal, where \(0^\circ < \theta < 90^\circ\), and subsequently reflects toward the vertical mirror. Which of the following diagrams correctly represents the complete path of the light ray and its reflections off both mirrors?

Two flat, planar mirrors are joined at a right angle (<span>90^</span>\(90^\circ\)). A ray of monochromatic light traveling in the plane of the page is incident on the horizontal mirror at an angle \(\theta\) relative to the surface normal, where \(0^\circ < \theta < 90^\circ\), and subsequently reflects toward the vertical mirror. Which of the following diagrams correctly represents the complete path of the light ray and its reflections off both mirrors?

![Two perpendicular thick gray line segments meet at the bottom-left corner to form a right angle: a horizontal segment labeled Mirror 1 along the bottom and a vertical segment labeled Mirror 2 along the left. A single straight solid line with an arrow pointing downward and to the left approaches Mirror 1. A vertical dashed normal line is drawn perpendicular to Mirror 1 at the point of contact, with the angle between the incoming ray and the vertical dashed line labeled \theta. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596707-P11bO4.jpg)

- **A.** A diagram where the ray reflects from the first mirror at angle \(\theta\) to the normal and exits the second mirror oriented perpendicular to the incident ray.
- **B.** A diagram where the ray reflects from the second mirror at angle \((90^\circ - \theta)\) relative to its normal, emerging parallel to the incident ray in the opposite direction.
- **C.** A diagram where the angle of incidence at the second mirror is labeled \(\theta\) relative to its normal, causing the outgoing ray to diverge at an angle of \(2\theta\) from the incident direction.
- **D.** A diagram where the ray retroreflects immediately from the first mirror back along its original path without reaching the second mirror.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123420/*