When an object is placed between the pole and the focus of a concave mirror, what is the position of the imag… - 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

When an object is placed very close to a concave mirror, specifically between its pole (the center of the mirror's surface) and the principal focus, the reflected light rays spread out or diverge.
These diverging rays cannot form a real image in front of the mirror. However, to an observer, they appear to originate from a point behind the mirror.
This apparent point of intersection behind the mirror is where the image is formed. Because the rays don't actually meet there, the image is 'virtual'.
The resulting image is upright (erect) and larger than the object (magnified). This principle is used in shaving mirrors and dental mirrors.

Option B: The position of the image formed by a mirror is always predictable based on the object's position and the mirror's properties, according to the laws of reflection.
Option C: Images are formed in front of a concave mirror only when they are real images. This occurs when the object is placed at the focus or anywhere farther away from the mirror than the focus.
Option D: An image is a projection formed by the convergence of light rays (or their virtual extensions). It cannot be formed on the physical surface of the mirror itself.

Visual 1: Ray Diagram. A ray diagram illustrating an object placed between the pole and focus of a concave mirror. It should clearly show two rays originating from the object: one parallel to the principal axis reflecting through the focus, and another hitting the pole and reflecting at an equal angle. The diagram must show the diverging reflected rays being extended backward to form a larger, upright, virtual image behind the mirror.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Image formation by a concave mirror as background academic context rather than a clinical decision trigger.
The principle of a concave mirror forming a magnified, virtual image is applied in various medical instruments.
ENT specialists use a head mirror (a concave mirror with a hole) to focus light into the patient's ear, nose, or throat, allowing them to see a magnified view of the area.
Dentists use small, handheld concave mirrors to get a magnified and upright view of teeth, helping them to spot cavities or other issues that are not easily visible.

How to Approach the Question

First, identify the key components of the question: the optical instrument is a 'concave mirror', and the object's location is 'between the pole and the focus'.
Recall the rules of image formation for a concave mirror. There are about six standard positions for the object, and each produces a different type of image.
This specific position (between pole and focus) is a special case. It is the only position that results in a virtual image for a concave mirror.
To confirm, visualize or sketch a simple ray diagram. A ray from the top of the object parallel to the axis will reflect through the focus. A ray hitting the center of the mirror (pole) will reflect at an equal angle. You will see that these reflected rays spread apart in front of the mirror.
Trace these diverging rays backward behind the mirror. The point where they appear to meet gives the position and size of the virtual image. This confirms the image is behind the mirror, erect, and magnified.

Concept Tested & Keywords

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