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प्रश्न
A 10 cm long stick is kept in front of a concave mirror having a focal length of 10 cm in such a way that the end of the stick closest to the pole is at a distance of 20 cm. What will be the length of the image?
उत्तर
Given:
Object distance u = −20 cm
Focal length f = −10 cm
Height of object h1 = 10 cm
Using the mirror formula and magnification relation,
`1/"f" = 1/"v" + 1/"u"` ...(mirror formula)
`1/(- 10) = 1/"v" + 1/(- 20)`
`1/"v" = 1/20 - 1/10`
`1/"v" = (10 - 20)/200`
`1/"v" = (- 10)/200`
`1/"v" = (- 1)/20`
∴ v = -20 cm
Magnification formula:
M = `"h"_2/"h"_1 = -("v")/"u"`
∴ `"h"_2/"h"_1 = - ((-20))/((- 20))`
∴ `"h"_2/10 = - ((-20))/((- 20))`
∴ h2 = −1 × 10
∴ h2 = −10 cm
∴ length of the image will be 10 cm and the image will be formed in front of a concave mirror its nature will be Real and Inverted.
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संबंधित प्रश्न
Write the spherical mirror formula and explain the meaning of each symbol used in it.
The mirror formula is ______.
Assertion: The mirrors used in torch lights are parabolic, not concave.
Reason: The image formed by a concave mirror is always virtual.
Assertion: The nature of the image depends on the size of the mirror.
Reason: Small mirrors always form a virtual image.
Which kind of mirrors are used in the shaving mirror? Why?
Which mirror is used as a reflector? Why?
Match the following:
| Column I | Column II | ||
| 1. | A plane mirror | a. | The image is erect & smaller in size than the object. |
| 2. | A concave mirror | b. | The image is erect & of the same size as the object. |
| 3. | A convex | c. | Used by dentists to see an enlarged image of teeth. |
| d. | Can form images of objects spread over a large area. |
Match the following:
| Column I | Column II | ||
| 1. | plane mirror | a. | Focal length is positive. |
| 2. | concave | b. | The focal length is negative. |
| 3. | convex | c. | The focal length is infinity. |
| 4. | Real image | d. | Magnification if positive value. |
| 5. | Virtual image | e. | Magnification if negative value. |
