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Questions
How will you differentiate between a convex and a concave lens by looking at
- a distant object,
- a printed page?
Differentiate between the virtual images formed by a convex lens and a concave lens on the basis of:
- object distance, and
- magnification.
Solution 1
- On seeing a distant object through the lens, if its inverted image is seen, then the lens is convex, and if the upright image is seen, then the lens is concave.
- On keeping the lens near a printed page, if the letters appear magnified, then the lens is convex, and if the letters appear diminished, then the lens is concave.
Solution 2
| Sr. No. | Basis | Convex lens | Concave lens |
| 1. | Object distance | As long as the item is within the focal length (i.e., closer to the lens than it is to the focal length), the lens will make a virtual image. | When you look at something through a concave lens, the image is always on the same side of the lens as the item, no matter how far away it is. |
| 2. | Magnification | When there is a virtual image (an item within the focal length) and a convex lens, the image stands up and is magnified (magnification > 1). | When you look through a concave lens, the picture you see is always straight up but smaller (magnification < 1). |
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