CBSE Class 10 Science 2021 Term 1 Solved Paper
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It consists of three cases followed by questions. There are a total of 12 questions (Q. No. 49 to 60 ) in this section. Attempt any 10 questions from this section. The first attempted 10 questions would be evaluated. P-Did not react eiter with cold or hot water but reacted with steam
Q- Reacted with hot water and the metal started floating
R - Reacted violently with cold water
S- Did not react with water at all
Based on the above observation answer the following:
Case-I:
A student, took four metals , and S and carried out different experiments to study the properties of metals. Some of the observation were:
- All metal could not be cut with knife except metal R.
- Metal P combined with oxygen to form an oxide which reacted with both acids and bases.
- Reaction with water.
Q- Reacted with hot water and the metal started floating
R - Reacted violently with cold water
S- Did not react with water at all
Based on the above observation answer the following:
Case-I:
A student, took four metals , and S and carried out different experiments to study the properties of metals. Some of the observation were:
- All metal could not be cut with knife except metal R.
- Metal P combined with oxygen to form an oxide which reacted with both acids and bases.
- Reaction with water.
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Question : 60 of 60
Marks:
+1,
-0
If power of the eyepiece is 5 diopters and it forms an image at a distance of from its optical centre, at what distance should the object be?
Solution:
Explanation: The relation between focal length and power of a lens is:
where is in dioptre and is in metre.
Since focal lens is positive, therefore it is a convex lens. In a convex lens, image formed is virtual when the object distance is less than the focal length.
Here, option (d) cannot be the answer because if object distance and focal length is also , the image should be formed at infinite but the image here is formed at . Now, in first three options, the object distance is less than the focal length which means that the image is virtual and is formed on the same side of the lens where the object is placed.
Therefore, according to sign conventions:
For finding the object distance, the lens formula is used. The lens formula is:
where is in dioptre and is in metre.
Since focal lens is positive, therefore it is a convex lens. In a convex lens, image formed is virtual when the object distance is less than the focal length.
Here, option (d) cannot be the answer because if object distance and focal length is also , the image should be formed at infinite but the image here is formed at . Now, in first three options, the object distance is less than the focal length which means that the image is virtual and is formed on the same side of the lens where the object is placed.
Therefore, according to sign conventions:
For finding the object distance, the lens formula is used. The lens formula is:
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