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If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objective
- a)100 cm
- b)10 cm
- c)20 cm
- d)25 cm
Correct answer is option 'A'. Can you explain this answer?
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Calculation of Focal Length of Objective Lens in an Astronomical Telescope
Given:
Tube length (L) = 105 cm
Magnifying power (M) = 20
Formula used:
Magnifying power (M) = focal length of objective lens (F) / focal length of eyepiece (f)
Calculation:
We know that magnifying power (M) = 20
Let the focal length of objective lens be F.
Using the formula,
M = F / f
20 = F / f
Since the normal setting is used, the final image is formed at infinity, and the eyepiece is adjusted to bring this image to the eye. Therefore, the final image is at the least distance of distinct vision (D) which is 25 cm.
Using the lens formula,
1/f = 1/D - 1/F
1/25 = 1/D - 1/F
1/F = 1/25 + 1/D
Substituting the value of F in the magnifying power formula,
20 = F / f
f = F / 20
Substituting the value of f in the lens formula,
1/F = 1/25 + 20/FL
Simplifying,
F = 100 cm
Therefore, the focal length of the objective lens in the astronomical telescope is 100 cm. Hence, option A is the correct answer.
Given:
Tube length (L) = 105 cm
Magnifying power (M) = 20
Formula used:
Magnifying power (M) = focal length of objective lens (F) / focal length of eyepiece (f)
Calculation:
We know that magnifying power (M) = 20
Let the focal length of objective lens be F.
Using the formula,
M = F / f
20 = F / f
Since the normal setting is used, the final image is formed at infinity, and the eyepiece is adjusted to bring this image to the eye. Therefore, the final image is at the least distance of distinct vision (D) which is 25 cm.
Using the lens formula,
1/f = 1/D - 1/F
1/25 = 1/D - 1/F
1/F = 1/25 + 1/D
Substituting the value of F in the magnifying power formula,
20 = F / f
f = F / 20
Substituting the value of f in the lens formula,
1/F = 1/25 + 20/FL
Simplifying,
F = 100 cm
Therefore, the focal length of the objective lens in the astronomical telescope is 100 cm. Hence, option A is the correct answer.
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If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objectivea) 100 cm b) 10 cm c) 20 cm d) 25 cm Correct answer is option 'A'. Can you explain this answer?
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If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objectivea) 100 cm b) 10 cm c) 20 cm d) 25 cm Correct answer is option 'A'. 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 If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objectivea) 100 cm b) 10 cm c) 20 cm d) 25 cm Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objectivea) 100 cm b) 10 cm c) 20 cm d) 25 cm Correct answer is option 'A'. Can you explain this answer?.
If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objectivea) 100 cm b) 10 cm c) 20 cm d) 25 cm Correct answer is option 'A'. 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 If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objectivea) 100 cm b) 10 cm c) 20 cm d) 25 cm Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objectivea) 100 cm b) 10 cm c) 20 cm d) 25 cm Correct answer is option 'A'. Can you explain this answer?.
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