Available Answers

1. 1.

   State, whether the following statements are true or false. Rewrite the false statement correctly.

   1. The lens which is thicker in the middle and thinner at the edges is called concave lens.
   2. A convex lens is used as a magnifying glass.
   3. The distance between focus and optical centre of a lens is called its focal length.
   4. A convex lens always forms a virtual, erect and diminished image when the object is placed in front of it.
   5. Concave lens is also called a converging lens.
   6. Divergent lens is a double concave lens.
2. 2.

   Fill in the blanks:

   1. _______________ is the lens which has one surface plane and the other concave.
   2. If the object is kept at the focal point of a convex lens, the image is formed at _______________.
   3. For a concave lens, the image formed is always _______________ irrespective of the position of object.
   4. _______________ lens is a converging lens.
   5. Virtual and magnified image is formed by _______________ lens.
   6. Virtual and enlarged image is formed by _______________ lens.
   7. Real image is obtained only by _______________ lens.
   8. _______________ lens gives _______________ image of same size.
   9. Real and diminished image is formed by _______________ lens.
   10. Convex lens is _______________ at the middle and _______________ at the edges.
   11. Concave lens is _______________ the edges and _______________ at the middle.
3. 3.

   Tick the appropriate answer :

   (a) A transparent material bounded by two curved surfaces is called

   1. Mirror
   2. Lens
   3. Telescope
   4. Microscope

   (b) A real, inverted and same size image is formed when object is placed at (for convex lens)

   1. 2F
   2. F
   3. Between F & 2F
   4. Infinity

   (c) A plano-concave lens has one face as concave and other face

   1. Convex
   2. Concave
   3. Plane
   4. None of the above

   (d) Concave lens forms an image which is :

   1. always real and diminished.
   2. real and of same size.
   3. virtual and smaller in size.
   4. virtual and magnified image.

   (e) Image formed by a concave lens is :

   1. real and of same size:
   2. real and magnified.
   3. virtual and diminished
   4. virtual and magnified image.
4. 4.

   Match the following:

   Position of image by a convex lens when object is placed at 2F Position of image by a convex lens when object is beyond 2F Position of image by a concave lens when object is beyond F A projector has Terrestrial telescope

   Concave lens At 2F Between F and 2F on the other side Between F and O on the same side. Convex lens

5. 5.

   Define 'centre of curvature'.

6. 6.

   Define 'radius of curvature'.