With the help of a ray diagram explain why a convex mirror is preferred for rear view mirrors in motor cars.
With the help of a ray diagram explain why a convex mirror is preferred for rear view mirrors in motor cars.
A convex mirror is preferred as a rear-view (wing) mirror in vehicles due to the following reasons:
- Always Erect Image: It always forms an erect (upright) image of the objects behind, which helps the driver quickly identify the orientation of trailing vehicles.
- Diminished Image (Wider Field of View): The images formed are diminished (smaller in size). Because the mirror is curved outwards, it has a much wider field of view compared to a plane or concave mirror. This allows the driver to monitor a significantly larger area of traffic behind them.
Ray Diagram
As shown in the diagram, rays coming from a wide angle are diverged and reflected into the driver's eye, compressing a wide field of view into a small mirror surface.
Marking Scheme
- 11 mark
- 21 mark
- 31 mark
Hint
Think about the shape of a convex mirror (curved outwards) and how this shape affects the direction of reflected rays and the size of the image formed.
Quick Oral Answer
Convex mirrors are used as rear-view mirrors because they are curved outwards, which gives them a wider field of view, and they always form erect, diminished images of the traffic behind.
Analysis & Explanation
According to the NCERT text, convex mirrors are preferred because they always give an erect, though diminished, image. Also, they have a wider field of view as they are curved outwards. Thus, convex mirrors enable the driver to view a much larger area than would be possible with a plane mirror. A plane mirror only shows a field of view equal to its physical size, whereas a convex mirror's outward curvature diverges incoming rays, allowing rays from extreme side angles to reach the observer's eye.
Common Mistakes
- 1Stating that a convex mirror forms a real image. It always forms a virtual, erect, and diminished image.
- 2Failing to mention the 'outward curvature' as the physical reason for the wider field of view.
Interesting Facts
Because of their wide field of view, large convex mirrors are also installed at sharp blind corners in hallways, parking lots, and roads to prevent collisions.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2011?
This question carries 3 marks in the CBSE Class 10 Science 2011 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Light — Reflection and Refraction" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Spherical Mirrors" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2011 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2011 paper.