State the changes in the position, size and nature of the image when the object is brought from infinity up to the convex lens. Illustrate your answer by drawing the ray diagrams.

State the changes in the position, size and nature of the image when the object is brought from infinity up to the concave lens. Illustrate your answer by drawing ray diagrams.

Identify the wrong statement.

1. For a convex lens, u is always negative.
2. For a convex lens, f is always positive.
3. For a convex lens, v is positive for a virtual image and negative for a real image.
4. For a concave lens, u, v and f all are negative.

For a convex lens,the value of magnification m is :

1. positive
2. negative
3. both positive as well as negative
4. none