Analyse the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations :
S.No. Object-Distance u (cm) Image-Distance v (cm) 1 - 100 + 25 2 - 60 + 30 3 - 40 + 40 4 - 30 + 60 5 - 25 + 100 6 - 15 + 120
(a) What is the focal length of the convex lens ? Give reason to justify your answer.
(b) Write the serial number of the observation which is not correct. On what basis have you arrived at this conclusion ?
(c) Select an appropriate scale and draw a ray diagram for the observation at S.No.2. Also find the approximate value of magnification.
Analyse the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations :
| S.No. | Object-Distance u (cm) | Image-Distance v (cm) |
|---|---|---|
| 1 | - 100 | + 25 |
| 2 | - 60 | + 30 |
| 3 | - 40 | + 40 |
| 4 | - 30 | + 60 |
| 5 | - 25 | + 100 |
| 6 | - 15 | + 120 |
(a) What is the focal length of the convex lens ? Give reason to justify your answer.
(b) Write the serial number of the observation which is not correct. On what basis have you arrived at this conclusion ?
(c) Select an appropriate scale and draw a ray diagram for the observation at S.No.2. Also find the approximate value of magnification.
Official answer
The given observation table is for a convex lens. However, the image-distance (v) is positive for all object-distances (u), which is not possible for a convex lens as it can form both real and virtual images.
Hint
The given observation table is for a convex lens. However, the image-distance (v) is positive for all object-distances (u), which is not possible for a convex lens as it can form both real and virtual images.
Analysis and explanation
The given observation table is for a convex lens. However, the image-distance (v) is positive for all object-distances (u), which is not possible for a convex lens as it can form both real and virtual images.
Question details
Q20 of 36 questions
- Board
- CBSE
- Class
- Class 10
- Subject
- Science
- Year
- 2017
- Section
- Section A
- Marks
- 5
- Type
- Long Answer
- Chapter
- Light — Reflection and Refraction
- Topic
- Refraction of Light
- Bloom's level
- Analyzing
- Syllabus topic
- Refraction of Light Through a Prism
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Frequently asked questions
How many marks does this question carry in CBSE Class 10 Science 2017?
This question carries 5 marks in the CBSE Class 10 Science 2017 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Light — Reflection and Refraction" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Refraction of Light" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2017 paper?
This is a Long Answer question from Section A in the CBSE Class 10 Science 2017 paper.