Uses of Spherical Mirrors - UNSOLVED PRACTICE SET
Chapter: Light Reflection and Refraction | Topic: Uses of Spherical Mirrors
USES OF SPHERICAL MIRRORS - UNSOLVED PRACTICE SET
Topic: Uses of Spherical Mirrors
Multiple Choice Questions
Q1. A dentist uses a concave mirror to examine a patient's tooth. The main reason is:
- It produces a real image of the tooth
- It magnifies the tooth when the tooth is placed between F and P
- It is easier to hold
- It produces a diminished image
Q2. Headlights of cars and torches use concave mirrors because:
- The object (bulb) is placed at the centre of curvature
- The bulb placed at the focus produces a powerful parallel beam
- They produce a diverging beam
- Convex mirrors are too expensive
Q3. The rear-view mirror in a car is a convex mirror because:
- It shows the real, inverted image of following vehicles
- It gives an erect, diminished image with a wider field of view
- It shows a larger image of vehicles behind
- It converges light efficiently
Q4. Solar cookers and solar furnaces use:
- Convex mirrors to focus sunlight
- Plane mirrors to reflect sunlight uniformly
- Concave mirrors to converge sunlight at the focal point
- Parabolic reflectors that are different from spherical mirrors
Q5. Large concave mirrors are used in reflecting telescopes because:
- They diminish far-away stars to visible size
- They collect and concentrate light from distant objects
- They produce virtual images of stars
- They are cheaper than lenses
Q6. The large mirrors used in security systems at shop entrances are:
- Concave - to give a magnified view
- Plane - to give a true-size view
- Convex - to give a wide-angle view of the entire shop
- Parabolic - to focus light on alarms
Short Answer Questions
Q7. Explain why a concave mirror is used by dentists and ENT doctors. At what position relative to the focus is the patient's body part placed, and what type of image is formed?
Q8. Explain the principle behind a car headlight reflector. Where is the bulb placed and what type of beam is produced? Why is this useful for driving at night?
Q9. Why is a convex mirror chosen as a rear-view mirror in vehicles rather than a plane or concave mirror? Discuss at least two reasons with reference to image properties.
Q10. A solar cooker in a rural Rajasthani home uses a large concave mirror.
(a) How does it cook food?
(b) Where is the cooking vessel placed?
(c) What property of a concave mirror makes it ideal?
Q11. Large astronomical reflecting telescopes (like the Devasthal telescope in Uttarakhand) use concave mirrors instead of lenses. Give two reasons why a large concave mirror is preferred over a large lens in telescopes.
Q12. A shopping mall in Mumbai installs a curved mirror at every corridor junction to prevent accidents.
(a) Which type of mirror is used?
(b) What property makes it suitable?
(c) Why not use a flat mirror for the same purpose?
Long Answer Questions
Q13. Describe in detail the uses of concave mirrors with the physics behind each use. Your answer must cover:
(a) use in torches and vehicle headlights (object at F → parallel beam),
(b) use by doctors (object between F and P → magnified virtual image),
(c) use in solar cookers and furnaces (parallel sunlight → focused at F),
(d) use in reflecting telescopes, and
(e) one additional application you can think of, justifying your choice using the image-formation properties of concave mirrors.
Q14. Compare the uses of concave and convex mirrors and explain why each type is chosen for its specific application. Present your comparison under:
(a) applications requiring magnification (which mirror and why),
(b) applications requiring a wide field of view (which mirror and why),
(c) applications requiring convergence of light (which mirror and why),
(d) one example each from Indian transport, Indian healthcare, and Indian domestic use, and
(e) is there any application where both types could be used but one is significantly better?
Q15. A student argues: 'Why don't vehicles use concave mirrors as rear-view mirrors? They can show bigger images of the cars behind, which would be safer.' Write a detailed response:
(a) Explain what image a concave mirror would form for a car 5 m behind (assuming f = 30 cm) — use mirror formula to find v and m.
(b) Explain why a magnified image is NOT safer in a rear-view mirror.
(c) Explain the field of view advantage of a convex mirror.
(d) Show using the mirror formula that a convex mirror of f = +30 cm gives a diminished image for the same car position (u = −500 cm).
(e) Conclude with the correct justification for using a convex mirror.
Numerical / Application-Based Problems
Q16. A car headlight uses a concave mirror of focal length 4 cm. The bulb is placed at the focus.
(a) Using the mirror formula, verify that parallel rays are produced (find v when u = −4 cm, f = −4 cm).
(b) If instead the bulb is placed 6 cm from the mirror (u = −6 cm), find v and m.
(c) What type of beam is produced now, and would this be useful in a headlight? Explain.
Q17. A dentist's concave mirror has f = −2 cm. A tooth is placed 1.5 cm from the mirror.
(a) Find the image distance v.
(b) Calculate magnification m.
(c) Describe the image fully.
(d) Why is this image useful for a dentist?
(e) What would happen if the tooth were moved to 3 cm from the mirror - recalculate and describe.
Q18. A convex security mirror of focal length +60 cm is installed at the entrance of a supermarket. A customer is standing 150 cm from the mirror.
(a) Find the image distance.
(b) Find the magnification.
(c) If the customer is 170 cm tall, find the image height.
(d) Explain qualitatively why this diminished image is actually beneficial for a security mirror.