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A person cannot see distinctly any object placed beyond 40cm from his eyes. Calculate the power of the lens which will help him to see distant objects clearly.
- a)+1 Dioptre
- b)-2.5 Dioptre
- c)-1.5 Dioptre
- d)+2 Dioptre
Correct answer is option 'B'. Can you explain this answer?
Most Upvoted Answer
A person cannot see distinctly any object placed beyond 40cm from his ...
A lens which can bring an object at infinity to 40 cm is required here.
So, u = infinity, v = -40 cm
We know, 1/f = 1/ v - 1/u
1/ f = 1/-40 - 1/infinity
So, f = -40 cm = -0. 4 m
Power of lens, P = 1/ f = 1/ -0. 4 = -2. 5 D
So, u = infinity, v = -40 cm
We know, 1/f = 1/ v - 1/u
1/ f = 1/-40 - 1/infinity
So, f = -40 cm = -0. 4 m
Power of lens, P = 1/ f = 1/ -0. 4 = -2. 5 D
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A person cannot see distinctly any object placed beyond 40cm from his ...
Given data:
Distance of the object = 40 cm
Distance of clear vision = infinity
We know that the formula for calculating the power of the lens is:
P = 1/f
where P is the power of the lens in dioptres and f is the focal length of the lens in meters.
Calculation:
As the person cannot see beyond 40 cm, we need to find the focal length of the lens that will help him see distant objects clearly.
Using the lens formula:
1/f = 1/v - 1/u
where v is the distance of clear vision (infinity) and u is the distance of the object (40 cm).
1/f = 1/infinity - 1/40 cm
1/f = 0 - 1/40 cm
1/f = -1/40 cm
f = -40 cm
The focal length of the lens is negative because the lens required is a concave lens (diverging lens) which has a negative focal length.
Now, using the formula P = 1/f, we get:
P = 1/-40 cm
P = -1/40 cm
P = -0.025 m^-1
P = -2.5 dioptres
Therefore, the power of the lens required to see distant objects clearly is -2.5 dioptres.
Distance of the object = 40 cm
Distance of clear vision = infinity
We know that the formula for calculating the power of the lens is:
P = 1/f
where P is the power of the lens in dioptres and f is the focal length of the lens in meters.
Calculation:
As the person cannot see beyond 40 cm, we need to find the focal length of the lens that will help him see distant objects clearly.
Using the lens formula:
1/f = 1/v - 1/u
where v is the distance of clear vision (infinity) and u is the distance of the object (40 cm).
1/f = 1/infinity - 1/40 cm
1/f = 0 - 1/40 cm
1/f = -1/40 cm
f = -40 cm
The focal length of the lens is negative because the lens required is a concave lens (diverging lens) which has a negative focal length.
Now, using the formula P = 1/f, we get:
P = 1/-40 cm
P = -1/40 cm
P = -0.025 m^-1
P = -2.5 dioptres
Therefore, the power of the lens required to see distant objects clearly is -2.5 dioptres.
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A person cannot see distinctly any object placed beyond 40cm from his eyes. Calculate the power of the lens which will help him to see distant objects clearly.a)+1 Dioptreb)-2.5 Dioptrec)-1.5 Dioptred)+2 DioptreCorrect answer is option 'B'. Can you explain this answer? for Class 10 2025 is part of Class 10 preparation. The Question and answers have been prepared according to the Class 10 exam syllabus. Information about A person cannot see distinctly any object placed beyond 40cm from his eyes. Calculate the power of the lens which will help him to see distant objects clearly.a)+1 Dioptreb)-2.5 Dioptrec)-1.5 Dioptred)+2 DioptreCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for Class 10 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A person cannot see distinctly any object placed beyond 40cm from his eyes. Calculate the power of the lens which will help him to see distant objects clearly.a)+1 Dioptreb)-2.5 Dioptrec)-1.5 Dioptred)+2 DioptreCorrect answer is option 'B'. Can you explain this answer?.
A person cannot see distinctly any object placed beyond 40cm from his eyes. Calculate the power of the lens which will help him to see distant objects clearly.a)+1 Dioptreb)-2.5 Dioptrec)-1.5 Dioptred)+2 DioptreCorrect answer is option 'B'. Can you explain this answer? for Class 10 2025 is part of Class 10 preparation. The Question and answers have been prepared according to the Class 10 exam syllabus. Information about A person cannot see distinctly any object placed beyond 40cm from his eyes. Calculate the power of the lens which will help him to see distant objects clearly.a)+1 Dioptreb)-2.5 Dioptrec)-1.5 Dioptred)+2 DioptreCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for Class 10 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A person cannot see distinctly any object placed beyond 40cm from his eyes. Calculate the power of the lens which will help him to see distant objects clearly.a)+1 Dioptreb)-2.5 Dioptrec)-1.5 Dioptred)+2 DioptreCorrect answer is option 'B'. Can you explain this answer?.
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