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प्रश्न
Numerical problem.
A concave mirror produces three times magnified real image of an object placed at 7 cm in front of it. Where is the image located? (Ans: 21 cm in front of the mirror)
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उत्तर
Given: hi = 3ho
u = 7 cm
Solution:
- m = `"h"_"i"/"h"_"O"⇒(3"h"_"o")/("h"_"O")` ∴ m = 3.
m = ` – v/u`
v = – m × u
= – 3 × 7 cm = – 21 cm.
Hence, Real, inverted and magnified image will be formed at 21 cm in front of the mirror.
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संबंधित प्रश्न
Why do we prefer a convex mirror as a rear-view mirror in vehicles?
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the questions that follow, without doing any calculations:
| S. No. | Object distance u(cm) | Image distance v(cm) |
| 1 | −90 | +18 |
| 2 | −60 | +20 |
| 3 | −30 | +30 |
| 4 | −20 | +60 |
| 5 | −18 | +90 |
| 6 | −10 | +100 |
(a) What is the focal length of the convex lens? Give reason in support of your answer.
(b) Write the serial number of that observation which is not correct. How did you arrive at this conclusion?
(c) Take an appropriate scale to draw ray diagram for the observation at S. No. 4 and find the approximate value of magnification.
An object is placed at a distance of 40 cm in front of a convex mirror of radius of curvature 40 cm. List four characteristics of the image formed by the mirror.
An object is placed at a long distance in front of a convex mirror of radius of curvature 30 cm. State the position of its image.
State whether the following statement is true or false:
A diverging mirror is used as a rear-view mirror.
Which type or mirror is usually used as a rear-view mirror in motor cars?
Give two uses of a convex mirror. Explain why you would choose convex mirror for these uses.
The radius of curvature of a convex mirror used as a rear view mirror in a moving car is 2.0 m. A truck is coming from behind it at a distance of 3.5 m. Calculate
- position and
- size of the image relative to the size of the truck.
- What will be the nature of the image?
Higher-Order Thinking Skills:
A convex mirror is in water. What should be the change in its focal length?
