Draw ray diagrams showing the image formation by a concave lens when an object is placed:
At the focus of the lens.

Identify the device used as a spherical mirror or lens in following cases, when the image formed is virtual and erect in each case.Object is placed between infinity and device, image formed is diminished and between focus and optical centre on the same side as that of the object.

A lens has a focal length of, -10cm. What is the power of the lens and what is its nature?

Describe with the help of a ray-diagram, the size, nature and position of the image formed by a convex lens when an object is placed beyond 2f in front of the lens.

The diagrams show the appearance of a fork when placed in front of and close to two mirrors A and B, turn by turn.

1. Which mirror is convex.
2. Which mirror is concave.

Give reasons for your choice.

Draw ray diagrams showing the image formation by a concave mirror when an object is placed:Between focus and centre of curvature of the mirror.

To find the image distance for varying object distances in case of a convex lens of focal length 15 cm, a student obtains on a screen a sharp image of a bright object by placing it at 20 cm distance from the lens. After that he gradually moves the object away from the lens and each time focuses the image on the screen.

1. In which direction-towards or away from the lens does he move the screen to focus the object?
2. How does the size of image change?
3. Approximately at what distance does he obtain the image of magnification -1?
4. How does the intensity of image change as the object moves farther and farther away from the lens?

Name the two types of spherical mirrors. What type of mirror is represented by the:

1. Back side of a shining steel spoon?
2. Front side of a shining steel spoon?

An object is placed at the following distance from a convex lens of focal length 15cm:

1. 35cm
2. 30cm
3. 20cm
4. 10cm

Which position of the object will produce:

1. A magnified real image?
2. A magnified virtual image?
3. A diminished real image?
4. An image of same size as the object?

To find-the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen.

1. In which direction - towards or away from the lens, does he move the screen to focus the object?
2. What happens to the size of the image - does it increase or decrease?
3. What happen when he moves the object very close to the lens?