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Concept:
- One of the surfaces of a mirror is polished and coated with silver nitrate.
- It reflects light falling on it.
- Plane mirror form only one virtual, erect, and same size image.
- If two mirrors are placed inclined at some angle more than one image is formed.
Explanation:
- In the given problem, mirrors are inclined at an angle of 30°
Θ = 30°
\(\frac{360^0}{\theta} = \frac{360}{30}=12 \), It is even no.
No of images formed is given by,
\(n=\frac{360^0}{\theta} -1=12 -1 \)
\(n=11\)
- 11 images are formed if the mirror is inclined at an angle of 30°.
- Option 2 is correct.
Additional Information
- The number of images formed due to two mirrors inclined at a different angle.
| Sr No | Value of \(\frac{360^0}{\theta}\) | Position of object | No of images formed(n) |
| 1 | Even | Symmetric | \(\frac{360^0}{\theta} -1 \) |
| 2 | Even | Asymmetric | \(\frac{360^0}{\theta} -1 \) |
| 3 | Odd | Symmetric | \(\frac{360^0}{\theta}-1 \) |
| 4 | Odd | Asymmetric | \(\frac{360^0}{\theta}\) |
- Images formed when two mirrors inclined at 45°
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Question 8 Exercise 7B
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Answer:
(a) The number of images formed when an object is placed between the two plane mirrors at an angle of 90°, is 3. Three images are formed.
We know that two mirrors kept perpendicular to each other, produce three images for an object that is placed in between them.
i.e, the angle between two mirrors is 60°, n=360°/90° = 4, number of images = n-1 = 4-1 = 3.
(b) The number of images formed if an object is placed between two plane mirrors with an angle of 60°, is five. Five images are formed:
i.e, the angle between two mirrors is 60°, n=360°/60° = 6, number of images = n-1 = 6-1 = 5.
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