SSC CGL 2025 Tier-I · 24 September 2025, Shift 2 · General Awareness · Question 16 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 13 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

The minimum number of rays required to locate the image formed by a spherical mirror is ______.

(a)One
(b)Two
(c)Three
(d)Four

Answer

Why

Correct — B. Each point of an object sends out countless rays, but you need just two. The image of a point forms where two reflected rays intersect, or appear to meet behind the mirror.

NCERT's Class 10 text says it directly: 'The intersection of at least two reflected rays give the position of image of the point object.' → option (b).

Why the others are wrong

(a)
One — A single reflected ray fixes only a line. The image lies somewhere along it, and without a second ray crossing it you cannot say where.
(c)
Three — A third ray is a useful check that the diagram is drawn right, but it is not needed. Two rays already cross at the image point.
(d)
Four — Four is the number of convenient rays NCERT describes: parallel to the axis, through the focus, through the centre of curvature, and at the pole. You choose any two of them.

Concept

A ray diagram locates an image without any calculation. Every point of an object is a source of rays, so you pick rays whose path after reflection you already know.

Where two such reflected rays meet, the image of that point forms and it is real. If they only appear to meet when extended behind the mirror, the image is virtual.

The stem asks for the minimum. Two rays suffice whether the image is real, in front of the mirror, or virtual, behind it.

Key facts

A ray parallel to the principal axis passes through the principal focus of a concave mirror after reflection, or appears to diverge from the focus of a convex mirror.
A ray through the principal focus of a concave mirror emerges parallel to the principal axis.
A ray through the centre of curvature is reflected back along its own path, because it strikes the mirror along the normal.
A ray striking the pole obliquely is reflected at an equal angle on the other side of the principal axis.

Study next

Images formed by a concave mirror for each object positionThe mirror formula and the New Cartesian sign conventionUses of concave and convex mirrors

Common traps

Answering four because four standard rays are taught. They are a menu to choose from, not a requirement.
Thinking a virtual image needs extra rays. Two reflected rays extended backwards locate it just as well.

Spherical mirrors are also asked at 21 Sep 2025, 09:00, GA Q.19 (the concave mirror of a solar furnace), and ray reasoning for a lens at 13 Sep 2024, 12:30, GA Q.2 (an object at the focus of a convex lens).

Related PYQs

No directly related past PYQ was found.

Topic: Scientific Research — all 220 SSC CGL questions on it, every solved shift.