Which one of the following is not true about the image formed by a plane mirror?

1. The Nature of Light and Reflection Laws (basic)

Light behaves like a ray that travels in straight lines—a property known as rectilinear propagation Science, Class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.158. When this light hits a highly polished surface like a mirror, it doesn't just pass through; it bounces back into the same medium. This phenomenon is called reflection. Whether the surface is flat (plane) or curved (spherical), the behavior of light is governed by two fundamental Laws of Reflection: first, the angle of incidence is always equal to the angle of reflection (∠i = ∠r); and second, the incident ray, the reflected ray, and the normal at the point of incidence all lie in the same plane Science, Class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.134.

A common conceptual hurdle is understanding what happens when light hits a mirror straight on. If a light beam falls on a mirror along the normal (perpendicular to the surface), the angle of incidence is 0°. Following the laws of reflection, the angle of reflection must also be 0°, causing the light to bounce back exactly along its original path Science, Class VIII (NCERT 2025 ed.), Light: Mirrors and Lenses, p.158.

When we look into a plane mirror, the image produced has very specific characteristics that are essential to master for Geometrical Optics:

Feature	Description
Nature	The image is virtual and erect. It cannot be projected onto a screen because light rays only appear to originate from behind the mirror Science, Class VIII (NCERT 2025 ed.), Light: Mirrors and Lenses, p.156.
Size	The image is exactly the same size as the object; there is no magnification.
Position	The image is formed as far behind the mirror as the object is in front of it.
Orientation	The image undergoes lateral inversion, meaning the left side of the object appears as the right side of the image.

Sources: Science, Class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.158; Science, Class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.134; Science, Class VIII (NCERT 2025 ed.), Light: Mirrors and Lenses, p.156; Science, Class VIII (NCERT 2025 ed.), Light: Mirrors and Lenses, p.158

2. Understanding Real vs. Virtual Images (intermediate)

In geometrical optics, the distinction between a real and a virtual image depends entirely on what the light rays are actually doing. A real image is formed when light rays coming from an object physically meet or converge at a specific point after reflection or refraction. Because the light rays truly pass through that point, these images can be captured on a screen, like the projection in a cinema hall. Mathematically, in our sign conventions, a real image is associated with a negative magnification because it is almost always inverted (upside down) Science, Light – Reflection and Refraction, p.143.

On the other hand, a virtual image is formed when light rays do not actually meet but only appear to diverge from a point behind the mirror or lens. If you were to place a screen at the position of a virtual image, nothing would appear on it because no light rays are actually striking that surface Science-Class VII, Light: Shadows and Reflections, p.161. This is why when you look into a plane mirror, you see yourself "inside" the mirror, but you cannot project that image onto a piece of paper held behind the glass. Virtual images are characterized by a positive magnification and are erect (upright) Science, Light – Reflection and Refraction, p.143.

Feature	Real Image	Virtual Image
Ray Behavior	Rays actually intersect.	Rays appear to diverge from a point.
Screen Test	Can be obtained on a screen.	Cannot be obtained on a screen.
Orientation	Generally inverted.	Generally erect (upright).

While some optical devices like convex lenses or concave mirrors can form both types of images depending on where the object is placed, others are more limited. For instance, a concave lens always produces a virtual, erect, and diminished image regardless of the object's distance Science, Light – Reflection and Refraction, p.153. Understanding this difference is crucial for mastering how cameras, telescopes, and even our own eyes process light to perceive the world.

Sources: Science, Class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.143; Science-Class VII, NCERT (Revised ed 2025), Light: Shadows and Reflections, p.161; Science, Class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.153

3. Spherical Mirrors: Concave and Convex (intermediate)

While a plane mirror reflects light from a flat surface, spherical mirrors have reflecting surfaces that are part of a hollow sphere. Imagine cutting a section out of a glass ball and silvering one side. Depending on which side you polish, you create one of two types: Concave or Convex. A simple way to visualize this is by looking at a stainless steel spoon. The side that holds your soup, curving inward, acts as a concave mirror, while the back of the spoon, bulging outward, acts as a convex mirror Science, Class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.135.

The Concave Mirror is often called a converging mirror because it bends parallel light rays inward toward a single point called the Principal Focus (F). Its behavior changes dramatically based on how close the object is to the mirror. If you place an object very close to it, the image appears enlarged and erect (upright). However, as you move the object further away, the image eventually flips upside down (inverted) and can vary in size Science, Class VIII, Light: Mirrors and Lenses, p.156. This versatility makes concave mirrors essential for shaving mirrors or dentist's tools, where a magnified view is needed.

In contrast, the Convex Mirror is a diverging mirror. Its reflecting surface curves outward, causing parallel rays to spread apart as if they were originating from a point behind the mirror. Unlike its concave cousin, a convex mirror is remarkably consistent: the image it forms is always virtual, erect, and diminished (smaller than the object) Science, Class VIII, Light: Mirrors and Lenses, p.156. This "shrinking" effect allows for a much wider field of view, which is why they are used as rear-view mirrors in vehicles to help drivers see a vast area behind them.

Feature	Concave Mirror	Convex Mirror
Reflecting Surface	Curved inwards (faces the center)	Curved outwards
Nature of Image	Can be real or virtual; enlarged or diminished	Always virtual, erect, and diminished
Common Use	Searchlights, Shaving mirrors, Solar furnaces	Rear-view mirrors, Vigilance mirrors in shops

Sources: Science, Class VIII . NCERT(Revised ed 2025), Chapter 10: Light: Mirrors and Lenses, p.155-156; Science, class X (NCERT 2025 ed.), Light – Reflection and Refraction, p.135-136

4. Practical Applications of Spherical Mirrors (exam-level)

Concept: Practical Applications of Spherical Mirrors

5. Refraction and Total Internal Reflection (TIR) (intermediate)

Concept: Refraction and Total Internal Reflection (TIR)

6. Characteristics of Images in Plane Mirrors (exam-level)

When we look into a plane mirror, we are observing a specific set of optical phenomena governed by the laws of reflection. The most fundamental characteristic is that the image is virtual and erect. Unlike a 'real' image which can be projected onto a screen, a virtual image is formed where light rays only appear to diverge from a point behind the mirror, rather than actually meeting there Science, Class X (NCERT 2025), Light – Reflection and Refraction, p.135. Because the rays don't physically converge, you can never place a piece of paper behind the mirror to 'capture' your reflection.

Geometrically, the image in a plane mirror is a perfect replica in terms of scale and positioning. Two key rules apply here:

• Size Parity: The size of the image is exactly equal to the size of the object. It is neither magnified nor diminished Science, Class VIII (NCERT 2025), Light: Mirrors and Lenses, p.156.
• Distance Symmetry: The image is formed as far behind the mirror as the object is in front of it. If you stand 2 meters from a mirror, your image is effectively 4 meters away from you (2m to the mirror + 2m behind it).

One of the most intriguing properties is lateral inversion. While the image is 'erect' (not upside down), it is reversed sideways. This means the left side of the object appears as the right side of the image, and vice versa. This is why the word 'AMBULANCE' is written in reverse on emergency vehicles—so that drivers looking in their plane rearview mirrors can read it correctly Science, Class VIII (NCERT 2025), Light: Mirrors and Lenses, p.156.

Characteristic	Description
Nature	Virtual and Erect (cannot be caught on screen)
Size	Same as the object (Magnification = 1)
Position	Object distance (u) = Image distance (v)
Orientation	Laterally inverted (Left ↔ Right)

Sources: Science, Class VIII (NCERT 2025), Light: Mirrors and Lenses, p.156; Science, Class X (NCERT 2025), Light – Reflection and Refraction, p.135

7. Solving the Original PYQ (exam-level)

Now that you have mastered the fundamental properties of light, this question serves as the perfect synthesis of your learning. To solve this, you must apply the laws of reflection and the critical distinction between real and virtual images. In a plane mirror, light rays do not actually intersect at a point after reflection; instead, they appear to diverge from a point behind the mirror. This is the very definition of a virtual image—it exists only in our perception and cannot be projected onto a screen. Therefore, the statement (C) It is real image is the only false characteristic among the choices and is the correct answer.

Let’s walk through the reasoning for the other options, which represent the hallmark traits of plane mirrors. One key principle you've studied is object-image symmetry: the size of the image is always identical to the object (Option A), and the image distance behind the mirror is exactly equal to the object distance in front of it (Option D). UPSC often uses these quantitative equalities to test your precision. If you remember that a plane mirror acts as a perfect mathematical reflection of the space in front of it, you can easily verify that options A, B, and D must be true.

A common trap in UPSC science questions is the concept of lateral inversion (Option B), where the left side of the object appears as the right side of the image. While it might feel like a distortion, it is a consistent property of plane mirror reflection. The trick to tackling "Which is NOT true" questions is to quickly identify the nature of the image first. Since a plane mirror image is always virtual and erect, any mention of it being a real image is an immediate red flag. As noted in Science, Class VIII. NCERT (Revised ed 2025), understanding that rays only appear to originate from behind the mirror is the key to debunking the idea of a real image.