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Two lenses of focal lengths 20cm and −40cm are held in contact. The image of an object at infinity will be formed by the combination at
- a)10 cm
- b)20 cm
- c)40 cm
- d)infinity
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
Two lenses of focal lengths 20cm and −40cm are held in contact. ...
Equivalent focal length is given by,
Here, f1 = 20cm and f2 = −40cm
⇒ f = 40cm
⇒ v = f = 40 cm [∵ u = ∞]
Here, f1 = 20cm and f2 = −40cm
⇒ f = 40cm
⇒ v = f = 40 cm [∵ u = ∞]
Most Upvoted Answer
Two lenses of focal lengths 20cm and −40cm are held in contact. ...
30cm are placed 40cm apart in air. Find the position of the image formed by the 20cm lens, when an object is placed 80cm in front of the 30cm lens.
To solve this problem, we can use the lens formula:
1/f = 1/v - 1/u
Where f is the focal length of the lens, v is the image distance, and u is the object distance.
First, let's calculate the image distance formed by the 30cm lens:
f = 30cm
u = 80cm
1/30 = 1/v - 1/80
Multiplying through by 240v:
8v = 240 - 3v
11v = 240
v = 21.82cm (approximately)
Now, let's calculate the object distance for the 20cm lens. The image formed by the 30cm lens will act as the object for the 20cm lens:
u = v = 21.82cm
Now, let's calculate the image distance formed by the 20cm lens:
f = 20cm
u = 21.82cm
1/20 = 1/v - 1/21.82
Multiplying through by 438.2v:
21.91v = 438.2 - 20v
41.91v = 438.2
v = 10.45cm (approximately)
Therefore, the position of the image formed by the 20cm lens is 10.45cm.
To solve this problem, we can use the lens formula:
1/f = 1/v - 1/u
Where f is the focal length of the lens, v is the image distance, and u is the object distance.
First, let's calculate the image distance formed by the 30cm lens:
f = 30cm
u = 80cm
1/30 = 1/v - 1/80
Multiplying through by 240v:
8v = 240 - 3v
11v = 240
v = 21.82cm (approximately)
Now, let's calculate the object distance for the 20cm lens. The image formed by the 30cm lens will act as the object for the 20cm lens:
u = v = 21.82cm
Now, let's calculate the image distance formed by the 20cm lens:
f = 20cm
u = 21.82cm
1/20 = 1/v - 1/21.82
Multiplying through by 438.2v:
21.91v = 438.2 - 20v
41.91v = 438.2
v = 10.45cm (approximately)
Therefore, the position of the image formed by the 20cm lens is 10.45cm.
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Two lenses of focal lengths 20cm and −40cm are held in contact. The image of an object at infinity will be formed by the combination ata)10 cmb)20 cmc)40 cmd)infinityCorrect answer is option 'C'. Can you explain this answer? for NEET 2025 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about Two lenses of focal lengths 20cm and −40cm are held in contact. The image of an object at infinity will be formed by the combination ata)10 cmb)20 cmc)40 cmd)infinityCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for NEET 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Two lenses of focal lengths 20cm and −40cm are held in contact. The image of an object at infinity will be formed by the combination ata)10 cmb)20 cmc)40 cmd)infinityCorrect answer is option 'C'. Can you explain this answer?.
Two lenses of focal lengths 20cm and −40cm are held in contact. The image of an object at infinity will be formed by the combination ata)10 cmb)20 cmc)40 cmd)infinityCorrect answer is option 'C'. Can you explain this answer? for NEET 2025 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about Two lenses of focal lengths 20cm and −40cm are held in contact. The image of an object at infinity will be formed by the combination ata)10 cmb)20 cmc)40 cmd)infinityCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for NEET 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Two lenses of focal lengths 20cm and −40cm are held in contact. The image of an object at infinity will be formed by the combination ata)10 cmb)20 cmc)40 cmd)infinityCorrect answer is option 'C'. Can you explain this answer?.
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