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The image of the source of light is formed by a convex lens on a screen at a distance of 20cm from the lens .on placing a second lens exactly at the middle of the lens and the screen,the screen had to shifted 15cm away to obtain image of the screen.calculate focal length of the second lens.?
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The image of the source of light is formed by a convex lens on a scree...
Given:
- Distance between the source of light and the convex lens = 20 cm
- Distance between the convex lens and the screen = 20 cm
- Distance by which the screen is shifted when the second lens is placed at the middle = 15 cm
To find:
- Focal length of the second lens
Explanation:
When a convex lens forms an image, the image can be formed either on the same side as the object (virtual image) or on the opposite side (real image). In this case, since the image is formed on the screen, it is a real image.
When the second lens is placed at the middle, the image distance changes. Let's analyze the situation step by step:
Step 1: Image Formation by the Convex Lens
- The distance between the object and the lens (u) = -20 cm (negative sign indicates that the object is on the same side as the incident light)
- The distance between the lens and the image (v) = 20 cm (since the image is formed on the screen)
- Using the lens formula: 1/f = 1/v - 1/u
- Substituting the values: 1/f = 1/20 - 1/-20
- Simplifying: 1/f = 1/20 + 1/20
- 1/f = 2/20
- 1/f = 1/10
- f = 10 cm
Step 2: Image Formation by the Second Lens
- The distance by which the screen is shifted (s) = 15 cm
- The distance between the second lens and the image of the screen (v') = 20 + 15 = 35 cm (since the screen is shifted away)
- The distance between the second lens and the image formed by the first lens (u') = 20 cm (as the screen was initially at a distance of 20 cm)
- Using the lens formula: 1/f' = 1/v' - 1/u'
- Substituting the values: 1/f' = 1/35 - 1/20
- Simplifying: 1/f' = (20 - 35)/(20 * 35)
- 1/f' = -15/(20 * 35)
- 1/f' = -3/(4 * 7)
- f' = -84/3
- f' = -28 cm
Conclusion:
The focal length of the second lens is -28 cm. The negative sign indicates that the second lens is a diverging lens.
- Distance between the source of light and the convex lens = 20 cm
- Distance between the convex lens and the screen = 20 cm
- Distance by which the screen is shifted when the second lens is placed at the middle = 15 cm
To find:
- Focal length of the second lens
Explanation:
When a convex lens forms an image, the image can be formed either on the same side as the object (virtual image) or on the opposite side (real image). In this case, since the image is formed on the screen, it is a real image.
When the second lens is placed at the middle, the image distance changes. Let's analyze the situation step by step:
Step 1: Image Formation by the Convex Lens
- The distance between the object and the lens (u) = -20 cm (negative sign indicates that the object is on the same side as the incident light)
- The distance between the lens and the image (v) = 20 cm (since the image is formed on the screen)
- Using the lens formula: 1/f = 1/v - 1/u
- Substituting the values: 1/f = 1/20 - 1/-20
- Simplifying: 1/f = 1/20 + 1/20
- 1/f = 2/20
- 1/f = 1/10
- f = 10 cm
Step 2: Image Formation by the Second Lens
- The distance by which the screen is shifted (s) = 15 cm
- The distance between the second lens and the image of the screen (v') = 20 + 15 = 35 cm (since the screen is shifted away)
- The distance between the second lens and the image formed by the first lens (u') = 20 cm (as the screen was initially at a distance of 20 cm)
- Using the lens formula: 1/f' = 1/v' - 1/u'
- Substituting the values: 1/f' = 1/35 - 1/20
- Simplifying: 1/f' = (20 - 35)/(20 * 35)
- 1/f' = -15/(20 * 35)
- 1/f' = -3/(4 * 7)
- f' = -84/3
- f' = -28 cm
Conclusion:
The focal length of the second lens is -28 cm. The negative sign indicates that the second lens is a diverging lens.
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The image of the source of light is formed by a convex lens on a screen at a distance of 20cm from the lens .on placing a second lens exactly at the middle of the lens and the screen,the screen had to shifted 15cm away to obtain image of the screen.calculate focal length of the second lens.?
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The image of the source of light is formed by a convex lens on a screen at a distance of 20cm from the lens .on placing a second lens exactly at the middle of the lens and the screen,the screen had to shifted 15cm away to obtain image of the screen.calculate focal length of the second lens.? for NEET 2024 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about The image of the source of light is formed by a convex lens on a screen at a distance of 20cm from the lens .on placing a second lens exactly at the middle of the lens and the screen,the screen had to shifted 15cm away to obtain image of the screen.calculate focal length of the second lens.? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for The image of the source of light is formed by a convex lens on a screen at a distance of 20cm from the lens .on placing a second lens exactly at the middle of the lens and the screen,the screen had to shifted 15cm away to obtain image of the screen.calculate focal length of the second lens.?.
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