The principal axis of a spherical mirror is \ \ \ \ \ . - RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

General Knowledge

Easy

Appeared in: RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Explanation

The principal axis is an imaginary straight line passing through the pole and the center of curvature of a spherical mirror.
The pole is the geometric center of the mirror's reflecting surface.
The center of curvature is the center of the sphere of which the mirror is a part.
Geometrically, any line drawn from the center of a sphere to its surface is perpendicular (normal) to the surface at that point.
Therefore, the principal axis, which connects the center and the pole, is normal to the mirror at its pole.

Option B: A line parallel to the mirror would, by definition, never intersect it. The principal axis must pass through the pole, which is on the mirror's surface.
Option C: The angle is not arbitrary. The principal axis is defined by its relationship to the center of curvature and the pole, which results in a perpendicular (90-degree) orientation to the tangent at the pole.
Option D: Similar to the 45-degree option, this is an incorrect angle. The geometric definition of the principal axis fixes its orientation as normal (perpendicular) to the mirror at the pole.

Visual 1: Diagram - A diagram of both a concave and a convex spherical mirror. It should clearly label the Pole (P), Center of Curvature (C), and the Principal Axis as the line passing through both points, showing it is perpendicular to the mirror surface at P.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Geometric Optics: Spherical Mirrors as background academic context rather than a clinical decision trigger.
This is a fundamental concept in physics (optics), not directly a clinical nursing question.
However, understanding basic optics is foundational for comprehending how various medical diagnostic instruments, such as ophthalmoscopes (for examining the retina) and endoscopes, function.
The principles of reflection and focusing are critical to the design and use of these tools for visualizing internal body structures.

How to Approach the Question

This is a factual recall question based on a definition in physics.
First, identify the key term in the question: 'principal axis of a spherical mirror'.
Recall the precise definition of the principal axis. It is the line connecting two key points: the pole (P) and the center of curvature (C).
Visualize the geometry of a sphere. A line from the center to the surface is always 'normal' (perpendicular) to the surface.
Apply this geometric rule to the definition. The principal axis must be normal to the mirror at the pole.
Evaluate the options based on this conclusion. 'Normal to the mirror at its pole' directly matches the definition. The other options (parallel, inclined at an angle) are geometrically incorrect.

Concept Tested & Keywords

QbMe_QK196qNBghTcsuVcm