What is the size of the image produced by a concave lens compared to the object?

RRB Nsg. Superintendent-2026 (Shift -2nd)

General Knowledge

Easy

Appeared in: RRB Nsg. Superintendent-2026 (Shift -2nd)

Explanation

A concave lens is a diverging lens, meaning it spreads out light rays that pass through it.
Because the light rays diverge, they never converge to form a real image. Instead, they appear to originate from a point on the same side of the lens as the object.
This results in an image that is always virtual, erect (upright), and diminished (smaller than the object), regardless of the object's distance from the lens.

Option A: An image of the same size is produced by a plane mirror, or by a convex lens only when the object is placed at twice the focal length (2F). A concave lens never produces a same-sized image.
Option B: Enlarged (larger) images are produced by convex (converging) lenses when the object is placed within the focal length. Concave lenses always produce diminished images.
Option D: Focal length is a property of the lens itself—a measure of distance that indicates its focusing power. It does not describe the relative size (magnification) of the image.

Visual 1: Ray Diagram - A ray diagram showing parallel light rays from an object passing through a concave lens, diverging, and forming a smaller, virtual image on the same side as the object.
Visual 2: Comparison Chart - An infographic comparing the types of images (real/virtual, erect/inverted, size) formed by concave and convex lenses for different object positions.

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 lens as background academic context rather than a clinical decision trigger.
Concave lenses are the primary tool used in eyeglasses and contact lenses to correct myopia (nearsightedness).
In a myopic eye, the natural lens focuses light in front of the retina, causing distant objects to appear blurry. The diverging effect of a concave lens spreads the light rays before they enter the eye, effectively moving the focal point backward onto the retina.
What if the patient had hyperopia (farsightedness)? A convex lens would be required. In hyperopia, the eye focuses light behind the retina, so a converging (convex) lens is needed to bend the light more strongly and move the focal point forward onto the retina.

How to Approach the Question

Identify the key component in the question: 'concave lens'.
Recall the fundamental properties associated with a concave lens. A key mnemonic is that it is a 'diverging' lens.
Connect the term 'diverging' to its physical meaning: it spreads light rays apart.
Reason that because the rays spread apart, they can only form a virtual image that appears smaller than the actual object.
Evaluate the given options. 'Smaller than the object' directly aligns with this recalled property.
Systematically eliminate the other options by recalling the conditions under which they are true (e.g., 'larger' for a convex lens, 'same size' for a plane mirror).

Concept Tested & Keywords

QSUwABCSU369-u6AyeKqCq