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 the focus and device, image formed is enlarged and on the same side as that of the object.

Name the type of mirror used by dentists. How does it help?

Explain with the help of a diagram, why a pencil partly immersed in water appears to be bent at the water surface.

If the magnification of an image formed by a mirror is positive, what does it mean?

A boy with a mouth 5cm wide stands 2m away from a plane mirror. Where is his image and how wide is the image of his mouth?

What kind of lens can form:

1. An inverted magnified image?
2. An erect magnified image?
3. An inverted diminished image?
4. An erect diminished image?

Refractive indices of four media A, B, C and D are given below:

Medium	Refractive index
A B C D	1.33 1.44 1.52 1.65

In which of these four media is the speed of light:

1. Maximum, and
2. Minimum?

Draw a ray diagram to show the formation of a virtual magnified image of an object by a convex lens. In your diagram, the position of object and image with respect to the principal focus should be shown clearly.

A convex lens of focal length 25cm and a concave lens of focal length 10cm are placed in close focal contact with each other. Calculate the lens power of this combination.

State the two laws of reflection of light.