A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths?
1)
-75, 50
2)
-10, 15
3)
75, 50
4)
-15, 10
A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths?
1)
-75, 50
2)
-10, 15
3)
75, 50
4)
-15, 10
Question ID - 100423 | SaraNextGen Top Answer
A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths?
1)
-75, 50
2)
-10, 15
3)
75, 50
4)
-15, 10
|
A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths? |
|||||||
|
1) |
-75, 50 |
2) |
-10, 15 |
3) |
75, 50 |
4) |
-15, 10 |
1 Answer
127 votes
Answer Key / Explanation : (4) -
Let focal length of convex lens is +f then focal length of concave lens would be 
.
From the given condition,
cm
Therefore, focal length of convex lens = + 10 cm and that of concave lens = -15 cm.
127 votes
Answer Link
127