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An eye specialist prescribes spectacles having combination of convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. The power of this lens combination in diopters is
(a) +1.5
  • a)
    +1.5
  • b)
    -1.5
  • c)
    +6.67
  • d)
    -6.67
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
An eye specialist prescribes spectacles having combination of convex l...
The focal length of combination is given by

or 

∴ Power of the combination in dioptres, 

= -1.5
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Most Upvoted Answer
An eye specialist prescribes spectacles having combination of convex l...
To find the power of the lens combination, we need to calculate the equivalent focal length of the combination by using the lens formula.

1. Finding the equivalent focal length:
The lens formula is given by:
1/f = 1/f1 + 1/f2
Where f1 is the focal length of the convex lens and f2 is the focal length of the concave lens.

Given:
f1 = 40 cm (convex lens)
f2 = -25 cm (concave lens)

Substituting these values into the lens formula:
1/f = 1/40 + 1/(-25)

Simplifying the equation:
1/f = (25 - 40)/(40*(-25))
1/f = -15/(-1000)
1/f = 1/66.67

Taking the reciprocal of both sides:
f = 66.67 cm

2. Calculating the power of the lens combination:
The power of a lens is given by the formula:
P = 1/f

Substituting the value of f:
P = 1/66.67
P ≈ 0.015 diopters

Since the power is positive, the correct answer is option (b) -1.5 diopters.

In conclusion, the power of the lens combination is -1.5 diopters.
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An eye specialist prescribes spectacles having combination of convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. The power of this lens combination in diopters is(a)+1.5a)+1.5b)-1.5c)+6.67d)-6.67Correct answer is option 'B'. Can you explain this answer?
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An eye specialist prescribes spectacles having combination of convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. The power of this lens combination in diopters is(a)+1.5a)+1.5b)-1.5c)+6.67d)-6.67Correct 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 An eye specialist prescribes spectacles having combination of convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. The power of this lens combination in diopters is(a)+1.5a)+1.5b)-1.5c)+6.67d)-6.67Correct 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 An eye specialist prescribes spectacles having combination of convex lens of focal length 40 cm in contact with a concave lens of focal length 25 cm. The power of this lens combination in diopters is(a)+1.5a)+1.5b)-1.5c)+6.67d)-6.67Correct answer is option 'B'. Can you explain this answer?.
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