Which one of the following isnottrue about the image formed by a plane mirror?
It is real image
Understanding Image Formation by a Plane Mirror
Let's analyze the properties of the image formed when you look at yourself in a plane mirror. A plane mirror is a flat, smooth reflective surface. When an object is placed in front of a plane mirror, an image is formed behind the mirror. We need to identify which statement about this image is not true.
Properties of the Image Formed by a Plane Mirror
The image formed by a plane mirror has several distinct characteristics. Let's examine the properties mentioned in the options:
- Size: The image formed is always the same size as the object. The magnification (ratio of image height to object height) is 1.
- Orientation: The image is upright (erect) relative to the object. However, it is laterally inverted.
- Lateral Inversion: This means that the left side of the object appears as the right side of the image, and vice versa. For example, if you raise your right hand, the image in the mirror appears to raise its left hand.
- Nature: The image formed by a plane mirror is virtual. This means that the light rays reflecting from the mirror do not actually converge at the location of the image; they only appear to diverge from that point behind the mirror. Because the rays do not physically meet, a virtual image cannot be projected onto a screen.
- Position: The image is formed as far behind the mirror as the object is in front of the mirror. The distance of the image from the mirror is equal to the distance of the object from the mirror. Also, the image is formed perpendicular to the mirror surface.
Analyzing the Given Statements
Let's evaluate each statement based on the properties we just discussed:
Statement 1: "It is of the same size as the subject"
This statement is true. The magnification of a plane mirror is exactly 1, meaning the image size is equal to the object size.
Statement 2: "It is laterally inverted"
This statement is true. Plane mirrors produce laterally inverted images. This is why ambulances often have "ECNALUBMA" written on the front.
Statement 3: "It is real image"
This statement is false. As explained earlier, the image formed by a plane mirror is virtual, not real. Real images are formed where light rays actually converge and can be projected onto a screen (like the image on a cinema screen). Virtual images, like the one in a plane mirror, are formed where rays only appear to diverge from, and cannot be projected onto a screen.
Statement 4: "It is formed as far behind the mirror as the object is in front"
This statement is true. The image distance (\(v\)) for a plane mirror is equal in magnitude to the object distance (\(u\)), i.e., \(|v| = |u|\). The image is located behind the mirror, at the same distance from the mirror surface as the object is in front.
Based on the analysis, the statement that is not true about the image formed by a plane mirror is that it is a real image. It is, in fact, a virtual image.
| Property | Description | True/False for Plane Mirror |
|---|---|---|
| Size | Same size as object (\(m=1\)) | True |
| Orientation | Upright (erect) | True |
| Inversion | Laterally inverted | True |
| Nature | Real vs. Virtual | Virtual |
| Position (Distance) | Image distance equals object distance (\(|v|=|u|\)) | True |
Revision Table: Plane Mirror Image Characteristics
| Characteristic | Description |
|---|---|
| Virtual | Cannot be projected onto a screen; formed where rays appear to originate. |
| Erect/Upright | Oriented the same way as the object (not upside down). |
| Same Size | Image height equals object height. |
| Laterally Inverted | Left and right are reversed. |
| Equidistant | Image is as far behind the mirror as object is in front. |
Additional Information: Real vs. Virtual Images in Optics
Understanding the difference between real and virtual images is fundamental in optics. Here's a quick comparison:
- Real Image: Formed when light rays actually converge at a point after reflection or refraction. Can be projected onto a screen. Examples include images formed by convex lenses (like in a projector) or concave mirrors (if the object is beyond the focal point).
- Virtual Image: Formed when light rays only appear to diverge from a point after reflection or refraction. The rays do not actually meet. Cannot be projected onto a screen. Examples include images formed by plane mirrors, convex mirrors, and concave lenses.
Plane mirrors always produce virtual images because the reflected rays diverge and appear to originate from a point behind the mirror.
Important Questions from Mirrors and Images
- Which of the following statements correctly describes the nature and position of the image formed by a convex mirror when a real object is placed at any position in front of it?
- A beam of parallel light, originating from a distant source, is first incident on a convex lens with focal length $f_2$.
Subsequently, the light passes through the lens and then reflects from a concave mirror having a focal length $f_1$.
The concave mirror is placed at a distance $d$ from the convex lens.
For the light rays to retrace their original path and ultimately emerge from the lens as a parallel beam heading back towards the distant source, the separation distance $d$ between the lens and the mirror must be: The total number of images formed by two mirrors inclined at 72° to each other when the object is placed unsymmetrically will be ___?
A short linear object of length b lies along the axis of a concave mirror of focal length f at a distance u from the pole of the mirror. The size of the image is ;
- A concave mirror of focal length $f$ produces an image $n$ times the size of the object. If the image is virtual, then the distance of the object from the mirror is:
