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A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?
a) 20cm
b) 40cm
c) 60cm
d) 80cm?
a) 20cm
b) 40cm
c) 60cm
d) 80cm?
Verified Answer
A convex lens is placed in contact with the plane mirror. A point obje...
Figure shows a convex lens placed in contact with a plane mirror. An axial point object is placed at a distance O at a distance,
OC = 20cm.
As the image I of the object coincides with O, the rays refracted first from the lens and then refracted by the plane mirror must be retracing their path. This would happen when rays refracted by the convex lens fall normally on the mirror I.e, the refracted rays form a beam parallel to principal axis of the lens. Hence the object O must be at the focus of the convex lens.
f = CO = 20 cm.
This question is part of UPSC exam. View all NEET courses
Most Upvoted Answer
A convex lens is placed in contact with the plane mirror. A point obje...
Given:
- Distance of the point object from the lens, u = 20 cm
- Image distance from the lens, v = -20 cm (as the image coincides with the object)
- Focal length of the lens, f = ?
Formula:
The lens formula is given by:
1/f = 1/v - 1/u
Calculation:
Substituting the given values into the lens formula, we have:
1/f = 1/(-20) - 1/20
Simplifying the equation, we get:
1/f = -1/20 - 1/20
1/f = -2/20
1/f = -1/10
Taking the reciprocal of both sides of the equation, we find:
f = -10
Answer:
The focal length of the convex lens is -10 cm.
- Distance of the point object from the lens, u = 20 cm
- Image distance from the lens, v = -20 cm (as the image coincides with the object)
- Focal length of the lens, f = ?
Formula:
The lens formula is given by:
1/f = 1/v - 1/u
Calculation:
Substituting the given values into the lens formula, we have:
1/f = 1/(-20) - 1/20
Simplifying the equation, we get:
1/f = -1/20 - 1/20
1/f = -2/20
1/f = -1/10
Taking the reciprocal of both sides of the equation, we find:
f = -10
Answer:
The focal length of the convex lens is -10 cm.
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A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?a) 20cmb) 40cmc) 60cmd) 80cm?
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A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?a) 20cmb) 40cmc) 60cmd) 80cm? for NEET 2024 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?a) 20cmb) 40cmc) 60cmd) 80cm? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?a) 20cmb) 40cmc) 60cmd) 80cm?.
A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?a) 20cmb) 40cmc) 60cmd) 80cm? for NEET 2024 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?a) 20cmb) 40cmc) 60cmd) 80cm? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A convex lens is placed in contact with the plane mirror. A point object at a distance 20cm on the axis of combination has its image coinciding with itself. What is the focal length of the lens ?a) 20cmb) 40cmc) 60cmd) 80cm?.
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