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A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?
- a)-6.5 D
- b)-1.5 D
- c)6.5 D
- d)1.5 D
Correct answer is option 'B'. Can you explain this answer?
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Most Upvoted Answer
A doctor advises a patient to use spectacles with a convex lens of foc...
Let the power of convex lens be P1.. P1=100/40=2.5 D P1=2.5D let the power of concave lens be P2.. P2= -100/25= -4D P2= -4D let combined the both values...we get; P1+P2=2.5-4= -1.5 D.
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Community Answer
A doctor advises a patient to use spectacles with a convex lens of foc...
Given:
Focal length of convex lens, f1 = 40 cm
Focal length of concave lens, f2 = -25 cm (negative because concave lens has negative focal length)
To find:
Power of the combination of lenses
Solution:
The power of a lens is defined as the reciprocal of its focal length. The unit of power is dioptre (D), which is equal to the reciprocal of the focal length measured in meters.
1. Power of convex lens:
Power of convex lens P1 = 1/f1
P1 = 1/0.4 m (since f1 is given in cm, convert it to m)
P1 = 2.5 D
2. Power of concave lens:
Power of concave lens P2 = 1/f2
P2 = 1/-0.25 m (since f2 is given in cm, convert it to m and add negative sign)
P2 = -4 D
3. Power of combination of lenses:
When two lenses are placed in contact, their powers add up.
P = P1 + P2
P = 2.5 D - 4 D
P = -1.5 D
Therefore, the power of the combination of lenses is -1.5 D.
Option (B) is the correct answer.
Focal length of convex lens, f1 = 40 cm
Focal length of concave lens, f2 = -25 cm (negative because concave lens has negative focal length)
To find:
Power of the combination of lenses
Solution:
The power of a lens is defined as the reciprocal of its focal length. The unit of power is dioptre (D), which is equal to the reciprocal of the focal length measured in meters.
1. Power of convex lens:
Power of convex lens P1 = 1/f1
P1 = 1/0.4 m (since f1 is given in cm, convert it to m)
P1 = 2.5 D
2. Power of concave lens:
Power of concave lens P2 = 1/f2
P2 = 1/-0.25 m (since f2 is given in cm, convert it to m and add negative sign)
P2 = -4 D
3. Power of combination of lenses:
When two lenses are placed in contact, their powers add up.
P = P1 + P2
P = 2.5 D - 4 D
P = -1.5 D
Therefore, the power of the combination of lenses is -1.5 D.
Option (B) is the correct answer.
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A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?a)-6.5 Db)-1.5 Dc)6.5 Dd)1.5 DCorrect answer is option 'B'. Can you explain this answer?
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A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?a)-6.5 Db)-1.5 Dc)6.5 Dd)1.5 DCorrect answer is option 'B'. Can you explain this answer? for NEET 2024 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?a)-6.5 Db)-1.5 Dc)6.5 Dd)1.5 DCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?a)-6.5 Db)-1.5 Dc)6.5 Dd)1.5 DCorrect answer is option 'B'. Can you explain this answer?.
A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?a)-6.5 Db)-1.5 Dc)6.5 Dd)1.5 DCorrect answer is option 'B'. Can you explain this answer? for NEET 2024 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?a)-6.5 Db)-1.5 Dc)6.5 Dd)1.5 DCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A doctor advises a patient to use spectacles with a convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. What is the power of the combination ?a)-6.5 Db)-1.5 Dc)6.5 Dd)1.5 DCorrect answer is option 'B'. Can you explain this answer?.
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