JEE Exam > JEE Questions > Two plano-concave lenses (1 and 2) of glass o...
Start Learning for Free
Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contact with their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination is
- a)convex lens of focal length 70 cm
- b)concave lens of focal length 70 cm
- c)concave lens of focal length 66.6 cm
- d)convex lens of focal length 66.6 cm
Correct answer is option 'C'. Can you explain this answer?
| FREE This question is part of | Download PDF Attempt this Test |
Verified Answer
Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 ha...
Now
Most Upvoted Answer
Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 ha...
Given data:
- Refractive index of glass lens, ng = 1.5
- Radii of curvature of lens 1, R1 = -25 cm (negative sign indicates concave surface)
- Radii of curvature of lens 2, R2 = -20 cm (negative sign indicates concave surface)
- Refractive index of liquid, nl = 4/3
To find: The combined lens is a concave lens of focal length.
Solution:
When two thin lenses are in contact with each other, the effective focal length of the combination can be calculated using the lens formula:
1/f = (ng - nl) * (1/R1 - 1/R2)
- Since the lenses are in contact, their separation is zero, and the space between them is filled with liquid. Therefore, the effective refractive index between the lenses will be that of the liquid, i.e., nl.
- When light travels from a medium with a higher refractive index to a medium with a lower refractive index (ng > nl), the lens behaves as a diverging lens or a concave lens.
Using the lens formula, we can calculate the effective focal length of the combination:
1/f = (1.5 - 4/3) * (1/-25 - 1/-20)
Simplifying the equation:
1/f = (-1/6) * (4/500 - 5/500)
1/f = (-1/6) * (-1/500)
1/f = 1/3000
f = 3000 cm
The focal length of the combination is 3000 cm or 30 m.
Since the combination behaves as a concave lens, the negative sign indicates that the focal length is negative, i.e., the combination is a concave lens of focal length -30 m or -3000 cm.
Therefore, the correct option is (c) concave lens of focal length 66.6 cm.
- Refractive index of glass lens, ng = 1.5
- Radii of curvature of lens 1, R1 = -25 cm (negative sign indicates concave surface)
- Radii of curvature of lens 2, R2 = -20 cm (negative sign indicates concave surface)
- Refractive index of liquid, nl = 4/3
To find: The combined lens is a concave lens of focal length.
Solution:
When two thin lenses are in contact with each other, the effective focal length of the combination can be calculated using the lens formula:
1/f = (ng - nl) * (1/R1 - 1/R2)
- Since the lenses are in contact, their separation is zero, and the space between them is filled with liquid. Therefore, the effective refractive index between the lenses will be that of the liquid, i.e., nl.
- When light travels from a medium with a higher refractive index to a medium with a lower refractive index (ng > nl), the lens behaves as a diverging lens or a concave lens.
Using the lens formula, we can calculate the effective focal length of the combination:
1/f = (1.5 - 4/3) * (1/-25 - 1/-20)
Simplifying the equation:
1/f = (-1/6) * (4/500 - 5/500)
1/f = (-1/6) * (-1/500)
1/f = 1/3000
f = 3000 cm
The focal length of the combination is 3000 cm or 30 m.
Since the combination behaves as a concave lens, the negative sign indicates that the focal length is negative, i.e., the combination is a concave lens of focal length -30 m or -3000 cm.
Therefore, the correct option is (c) concave lens of focal length 66.6 cm.
Attention JEE Students!
To make sure you are not studying endlessly, EduRev has designed JEE study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in JEE.
|
Explore Courses for JEE exam
|
|
Similar JEE Doubts
Top Courses for JEEView all
Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer?
Question Description
Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer?.
Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer?.
Solutions for Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? in English & in Hindi are available as part of our courses for JEE.
Download more important topics, notes, lectures and mock test series for JEE Exam by signing up for free.
Here you can find the meaning of Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of
Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer?, a detailed solution for Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? has been provided alongside types of Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? theory, EduRev gives you an
ample number of questions to practice Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contactwith their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then the combination isa)convex lens of focal length 70 cmb)concave lens of focal length 70 cmc)concave lens of focal length 66.6 cmd)convex lens of focal length 66.6 cmCorrect answer is option 'C'. Can you explain this answer? tests, examples and also practice JEE tests.
|
|
Explore Courses for JEE exam
|
|
Suggested Free Tests
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
|
© EduRev
|
Education Revolution
|
Follow Us
|
Signup to see your scores
go up within 7 days!
Access 1000+ FREE Docs, Videos and Tests
Takes less than 10 seconds to signup