What is Convex Mirror? - Image Formation on a Convex Mirror
Science is an application-based subject where almost every topic that is read and learnt can be observed in our daily lives. Physics is the study of matter that includes an understanding of how the universe behaves through space and time. Physics is an important subject as it studies and deals with objects that surround us and is used by us like lenses, mirrors, electricity, energy, management of resources etc. In this article, students will learn about one such important topic of Physics that is, mirror, especially the convex mirror and its uses, and image formation on the convex mirror.
What is a Convex Mirror?
Mirrors are surfaces that reflect light creating images of objects in front of them. They are made by painting one surface of the glass with metal amalgams (mostly silver). Mirrors are of three types-
Plane Mirror – It is a flat mirror.
Spherical Mirror – It is of two types, concave and convex mirror.
Convex Mirror
It is a spherical mirror that is curved outward. It is cut out from a glass sphere, and its one surface is painted.
The principal axis is the imaginary line passing through exactly half the height of the convex mirror. All the rays parallel to the principal axis falling on the surface of the convex mirror seem to meet at a point (on the other side of the mirror). The point is known as the focus or focal point.
The point of intersection between the mirror and the principal axis is called the pole. The distance between the pole and the focus is known as the focal length. The centre of the glass spheres the mirror has been cut from is called the centre of curvature. It is an imaginary point. The distance between the pole and the centre of curvature is known as the radius of curvature. The radius of curvature is double the focal length.
A convex mirror can also be called a diverging mirror. This is because all the rays falling on its surface seem to be diverging from one point, which is the focus.
Image Formation on a Convex Mirror
The images formed by a convex mirror are always virtual, upright and diminished. Hence everything appears smaller. Compared to other reflective mirrors, the field of view for a convex mirror is the maximum. This is because the rays of light falling parallel diverge after reflection. Therefore, it covers a larger field of view compared to a plane or concave mirror. This one factor allows a very large usage of convex mirrors.
Uses of Convex Mirror
Convex mirrors are used in the rear-view mirrors of all the vehicles. They give a larger view when compared to plane mirrors. We will need huge plane mirrors to cover the width seen through a convex mirror of a much smaller size.
Convex mirrors are also used for security purposes in building hallways, in shops, etc. In a shop, one security personnel can view a wide part of the shop using convex mirrors put on the ceiling. Instead of having more than one security personnel, we can use multiple convex mirrors on the ceiling. In hallways, they are put at intersections or at blind spots in the corridors to improve the visibility for people walking there.
On roads, driveways, and alleys there are convex mirrors angularly kept especially at curves and turns to improve visibility. They are also used in parking lots to make parking and taking out of parking easy. The mirror helps them lookout at any incoming traffic or vehicles.
In automated teller machines, there is a convex mirror present close to the top of the machine. This is so that one can see what is behind their back. You can see if anyone is looking while you are entering your pin.
It can be used in sunglasses. It is used in such a way that all the rays of the sun are directed away from the person's eye.
Convex mirrors are also used in making magnifying glasses. Two convex mirrors are placed back to back to create the magnified effect.
They are used in street lights as they are good reflectors of light. They increase the amount of light; this makes it easier to light up streets with low energy usage.
They are used in telescopes too.
FAQs on Uses of Convex Mirror
1. What is a convex mirror and how does it form images?
A convex mirror is a type of spherical mirror with an outward-curved reflecting surface. It always forms virtual, upright, and diminished images because the reflected rays diverge and appear to come from a point behind the mirror. The image is always formed between the pole and the focal point, making objects look smaller but covering a wider field of view.
2. List the main uses of convex mirrors in daily life.
Convex mirrors are widely used due to their ability to provide a broader view. Main uses include:
- Vehicle rear-view mirrors for enhanced field of vision
- Security mirrors in shops, hallways, and at intersections
- Road safety at blind curves and driveways
- ATMs for user safety by allowing users to see behind them
- Street lights for efficient light distribution
- Telescopes and some magnifying glasses
3. Why are convex mirrors preferred over plane mirrors for vehicle rear-view mirrors?
Convex mirrors are preferred for vehicle rear-view mirrors because they cover a larger area, allowing the driver to see more of the road behind. Even though the images are smaller, this wide field of view helps spot vehicles and obstacles quickly, enhancing safety and enabling better judgment while driving.
4. How does a convex mirror improve visibility at road intersections and parking lots?
At intersections and parking lots, convex mirrors are positioned to allow drivers and pedestrians to see around corners or blind spots. This wider field of vision helps prevent collisions by making it easier to detect oncoming vehicles or people.
5. Explain how convex mirrors are used for security and surveillance purposes.
In security and surveillance, convex mirrors provide a panoramic view of a large area, even from a single spot. They are installed in shops, malls, and building corridors so that one person can monitor wide spaces efficiently, reducing blind spots and improving preventive measures.
6. What type of image is always formed by a convex mirror? Explain its characteristics.
A convex mirror always forms a virtual, erect, and diminished image. The image appears behind the mirror and cannot be projected on a screen. Due to this, objects look smaller than their actual size but can be seen along with their surroundings.
7. Can convex mirrors form real images? Why or why not?
Convex mirrors cannot form real images because the reflected rays always diverge after bouncing off the surface. These rays only appear to meet when extended backward, which creates a virtual image behind the mirror, not on a screen.
8. Why are convex mirrors called diverging mirrors?
They are called diverging mirrors because the incident parallel rays of light diverge after reflecting from the surface. This characteristic causes the images to appear diminished and virtual, which is used in applications where a wider field of vision is needed.
9. How do convex mirrors enhance the efficiency of street lighting?
Convex mirrors are used in street lighting as reflectors. Their curved surface spreads the light from the lamp over a wider area, increasing brightness and reducing the number of lights needed, thereby saving energy and improving coverage.
10. What would happen if a concave mirror replaced a convex mirror for road safety at a blind curve?
If a concave mirror was used instead of a convex mirror at a blind curve, the mirror would reflect a narrower and possibly inverted image, limiting the field of view. This could increase the risk of accidents, as users might not be able to see approaching vehicles effectively.
11. In what way does the use of convex mirrors in telescopes differ from their use in security systems?
In telescopes, convex mirrors help gather and direct more light from distant objects, aiding in the construction of wide-field reflecting telescopes. In security systems, convex mirrors are positioned to give a wide-angle view of a local area for surveillance, making them helpful in monitoring broad interior or exterior spaces.
12. How does the principle axis and focal point influence image formation by a convex mirror?
The principal axis is the central line through the mirror, with the focal point lying behind the mirror. Rays parallel to the principal axis appear to diverge from the focal point after reflection, ensuring the image is always virtual, diminished, and upright, regardless of the object's position in front of the mirror.
13. Discuss potential misconceptions about images formed by convex mirrors in the context of CBSE curriculum.
A common misconception is that convex mirrors can form real images or that they provide a true-size image like plane mirrors. In reality, convex mirrors always form smaller, virtual images and never real ones, which is essential to understand for solving numerical and conceptual questions in the CBSE syllabus.
