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A convex lens (of focal length 20 cm) and a concave mirror, having their principalaxes along the same lines, are kept 80 cm apart from each other. The concavemirror is to the right of the convex lens. When an object is kept at a distance of 30cm to the left of the convex lens, its image remains at the same position even if theconcave mirror is removed. The maximum distance of the object for which thisconcave mirror, by itself would produce a virtual image would be
  • a)
    10 cm
  • b)
    20 cm
  • c)
    30 cm
  • d)
    25 cm
Correct answer is option 'A'. Can you explain this answer?
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A convex lens (of focal length 20 cm) and a concave mirror, having the...
Focal length of concave mirror is 10cm
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A convex lens (of focal length 20 cm) and a concave mirror, having the...
As per the question, the image formed by the lens must have been formed at the centre of curvature of the concave mirror (the reason for image distance remaining unaffected by the presence of the mirror). So putting lens equation, we get image distance as v= 60cm. Now distance of image from the concave mirror is 20cm (80-60). This must be the radius of curvature of the mirror. Hence focal length of the mirror is 10cm. We know that if an object is kept between the focus and pole of a concave mirror, a virtual image is produced by it. Thus, max distance from the mirror which can form a virtual image is 10cm.
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A convex lens (of focal length 20 cm) and a concave mirror, having the...
Given information:
- Focal length of convex lens = 20 cm
- Distance between convex lens and concave mirror = 80 cm
- Object distance from convex lens = 30 cm
- Image distance from convex lens when concave mirror is removed = 30 cm

Explanation:
- The image distance remains the same when the concave mirror is removed, which means the concave mirror does not affect the image formed by the convex lens.
- When the concave mirror is removed, the convex lens alone forms the image at the same position as the object.
- This implies that the convex lens forms a virtual image for the object located at a distance of 30 cm.
- The formula for the lens formula is: $\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$, where f is the focal length, v is the image distance, and u is the object distance.
- For a virtual image formed by the convex lens, the object distance (u) must be less than the focal length (f) of the lens.
- Hence, the maximum distance of the object for which the concave mirror by itself would produce a virtual image is equal to the focal length of the convex lens, which is 20 cm.
Therefore, the correct answer is option A) 10 cm.
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A convex lens (of focal length 20 cm) and a concave mirror, having their principalaxes along the same lines, are kept 80 cm apart from each other. The concavemirror is to the right of the convex lens. When an object is kept at a distance of 30cm to the left of the convex lens, its image remains at the same position even if theconcave mirror is removed. The maximum distance of the object for which thisconcave mirror, by itself would produce a virtual image would bea)10 cmb)20 cmc)30 cmd)25 cmCorrect answer is option 'A'. Can you explain this answer?
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A convex lens (of focal length 20 cm) and a concave mirror, having their principalaxes along the same lines, are kept 80 cm apart from each other. The concavemirror is to the right of the convex lens. When an object is kept at a distance of 30cm to the left of the convex lens, its image remains at the same position even if theconcave mirror is removed. The maximum distance of the object for which thisconcave mirror, by itself would produce a virtual image would bea)10 cmb)20 cmc)30 cmd)25 cmCorrect answer is option 'A'. Can you explain this answer? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about A convex lens (of focal length 20 cm) and a concave mirror, having their principalaxes along the same lines, are kept 80 cm apart from each other. The concavemirror is to the right of the convex lens. When an object is kept at a distance of 30cm to the left of the convex lens, its image remains at the same position even if theconcave mirror is removed. The maximum distance of the object for which thisconcave mirror, by itself would produce a virtual image would bea)10 cmb)20 cmc)30 cmd)25 cmCorrect answer is option 'A'. Can you explain this answer? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A convex lens (of focal length 20 cm) and a concave mirror, having their principalaxes along the same lines, are kept 80 cm apart from each other. The concavemirror is to the right of the convex lens. When an object is kept at a distance of 30cm to the left of the convex lens, its image remains at the same position even if theconcave mirror is removed. The maximum distance of the object for which thisconcave mirror, by itself would produce a virtual image would bea)10 cmb)20 cmc)30 cmd)25 cmCorrect answer is option 'A'. Can you explain this answer?.
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