When a light ray falls on a surface, then it can undergo one of the three phenomena, namely, reflection, refraction, and absorption. Most of the light gets absorbed when a ray of light falls on a normal surface. Therefore, we can say that mirrors are polished surfaces, which are coated with Mercury (chemical symbol Hg) so that they can reflect most of the light that falls upon them. We can classify mirrors as a convex mirror, concave mirror, or a plane mirror, based on the reflecting surface. For forming an image with the help of a plane mirror, we require at least two rays of light from an object that either meet or appear to meet at a point. So, let's make ourselves familiar with the concepts of a plane mirror, along with its characteristics, uses, and applications.
Real Image and Virtual Image
A real image is an image that is produced either due to reflection or refraction when the ray of light arises from an object and then converges to a certain point. As the real image is a result of the actual intersection of a light ray, it can be captured on screen. The real image is always inverted and can be produced with a converging (convex) lens and a concave mirror.
A virtual image is an image that is produced when the ray of light arising from an object appears to strike at a certain definite point. As the virtual image is an imaginary intersection of the ray of light, it can never be captured on a screen. The virtual image is always erect and can be produced with a diverging (concave) lens, a convex mirror, and a plane mirror.
Hence, we can conclude by saying that a real image is captured on the screen, and it appears to be on the same side as the object. On the other hand, a virtual image can never be captured or obtained on a screen, and it appears to be on the opposite side as that of the mirror.
Characteristics and Features of the Image formed by a Plane Mirror
A plane mirror has various exclusive features and characteristics corresponding to the image that it forms, which are as follows:
A plane mirror always forms a virtual image. A virtual image is produced when the light rays from a source don’t cross or meet at a point to form an image.
The image formed or produced by a plane mirror is always of the same size as that of the object. A plane mirror always produces images that have a magnification of '1.' Also, the distance between the object and the mirror is equal to the distance between the mirror and the image. Besides, the image formed is also erect.
Another exclusive characteristic of the image formed by a plane mirror states that the image is laterally inverted, which implies that if you raise your left hand, it would appear in the plane mirror as if you have raised your right hand.
Applications and Uses of Plane Mirrors
Without any second thought, the invention of mirrors is indeed the greatest contribution to humankind. Almost every other person uses mirrors in their day-to-day lives for a variety of reasons. Also, we already know that plane mirrors are primarily used to see the reflection of an object. A plane mirror has several different uses and applications, including periscopes and kaleidoscopes, automobiles, shaving mirrors, dentists' mirror, torch lights, solar cookers, and security-related purposes.
Plane Mirrors - Used in Periscopes and Kaleidoscopes
While making kaleidoscopes, which are immensely loved by children, and periscopes, which are exclusively used in submarines, plane mirrors are widely used. The plane mirrors used in periscopes in submarines reflect the images of all the ships that are present on the surface of the water. The plane mirrors and colour glass used in kaleidoscopes reflect many colourful patterns.
Plane Mirrors - Used in Automobiles
For reflecting powerful beams of parallel light, vehicles widely used mirrors in their headlights. Furthermore, the prime use of a convex mirror in automobiles is that of the rearview mirrors since it always forms an erect image and gives a wider field of view due to its outward curve.
Plane Mirrors - Used in Torchlights
Plane mirrors are widely used in flashlights and torchlights for reflecting the light beams and are even used for the same purpose in the overhead projectors. With such uses and applications of the plane mirrors in the torchlights, they can be used at night and in dark places for finding or searching for things.
Plane Mirrors - Used as Shaving Mirrors
After waking up every morning, the first thing we do is look at ourselves in the mirror for several different purposes, including brushing, shaving, doing makeup, etc. Without the mirrors, it would have been extremely difficult for us to manage such things. Also, the concave mirrors are used as shaving mirrors to see a larger view or image of the face.
Plane Mirrors - Used by Dentists
Dentists widely use mirrors while performing for seeing the images of teeth and examining them. The plane mirrors are also exclusively used in microscopes to reflect the image of the object that is being monitored.
Plane Mirrors - Used in Solar Cookers
Plane mirrors are used in solar cookers as they are capable of reflecting most of the sunlight or sun rays that fall on their surface. Without any doubt, the solar cooker is the most effective and efficient way of utilizing a renewable source of energy for cooking-related purposes.
Plane Mirrors - Used for Safety and Security
Plane mirrors are widely used for finding the explosives underneath the vehicles. They are also used in shops and stores to keep an eye on the customers and prevent cases of robbery. Even on the blind turns of busy roads, mirrors are used to see the vehicles coming from the opposite side.
FAQs on Uses of Plane Mirrors
1. What is a plane mirror and what are its main characteristics according to the NCERT syllabus?
A plane mirror is a mirror with a flat (planar) reflective surface. When light rays strike this surface, they reflect in such a way that the angle of incidence equals the angle of reflection. The key characteristics of the image formed by a plane mirror are:
- Virtual: The image cannot be projected onto a screen because the light rays only appear to diverge from the image location.
- Erect: The image is upright, not inverted.
- Same Size: The size of the image is identical to the size of the object.
- Same Distance: The image is located as far behind the mirror as the object is in front of it.
- Laterally Inverted: The image is reversed from left to right. For example, your right hand appears as the left hand in the mirror's image.
2. What are the most common uses of a plane mirror in our daily lives?
Plane mirrors are fundamental in many everyday applications due to their ability to produce clear, undistorted images. Some important uses include:
- Looking Glasses: The most common use is as a personal grooming tool in bathrooms and dressing rooms to see our reflection.
- Periscopes: Used in submarines and trenches, periscopes use two parallel plane mirrors, typically angled at 45 degrees, to see over obstacles.
- Kaleidoscopes: This toy uses three or more plane mirrors joined together to create beautiful, symmetrical patterns through multiple reflections of coloured objects.
- Solar Cookers: Plane mirrors are used to reflect and concentrate sunlight onto a single point to generate heat for cooking.
- Security and Visibility: They are often used in shops to help monitor blind spots and on dangerous road turns to show oncoming traffic.
3. How does a plane mirror form an image?
A plane mirror forms an image through the process of regular reflection. Light rays originating from an object travel in straight lines towards the mirror. When these rays strike the mirror's flat surface, they reflect according to the laws of reflection. To an observer, these reflected rays appear to be coming from a point located behind the mirror. The brain interprets these diverging rays as an image at that point of apparent origin. Because the rays do not actually converge there, the image is virtual and cannot be caught on a screen.
4. Why does an image in a plane mirror appear to be laterally inverted?
Lateral inversion is a common point of confusion. The mirror does not actually swap left and right; it reverses the image front-to-back along the axis perpendicular to the mirror. For example, if you point towards a mirror, your finger in the reflection points back at you. This front-to-back reversal makes our brain perceive it as a left-right swap. If you write a word on a transparent sheet and face it towards the mirror, you will see it correctly, but if you turn the sheet to face yourself, the writing appears reversed—this is the same effect the mirror produces.
5. How does the image formed by a plane mirror differ from images formed by concave or convex mirrors?
The primary difference lies in the nature and variability of the image. A plane mirror always forms an image that is virtual, erect, and the same size as the object, regardless of the object's position. In contrast:
- A concave mirror (converging) can form either real, inverted images or virtual, erect, and magnified images, depending on how close the object is to the mirror.
- A convex mirror (diverging) always forms an image that is virtual, erect, and diminished (smaller than the object). This property provides a wider field of view, which is why it is used in car side-view mirrors.
6. What is the fundamental difference between a real and a virtual image?
The fundamental difference between a real and a virtual image relates to how the light rays behave after reflection or refraction.
- A real image is formed where light rays actually converge or meet at a point. It is always inverted and can be projected onto a screen. Real images are typically formed by concave mirrors and convex lenses.
- A virtual image is formed where light rays only appear to diverge from a point. It cannot be projected onto a screen and is always erect. All types of mirrors (plane, concave, and convex) can form virtual images under certain conditions.
7. What would happen if the reflecting surface of a plane mirror was not perfectly smooth?
If the reflecting surface of a plane mirror was not perfectly smooth at a microscopic level, it would cause diffuse reflection instead of regular reflection. In diffuse reflection, parallel light rays striking the uneven surface are reflected in many different directions. As a result, the mirror would not form a clear, recognisable image. Instead, it would scatter the light, and you would only see a lit-up, blurry surface, much like looking at a piece of white paper or a frosted glass window.
