Why does a beam of light when it enters glass at an angle? Why does it not bend if it inters the glass at right angles?

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

Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray of light parallel to the principal axis of a convex mirror and show the angle of incidence and angle of reflection on it.

An object 1cm tall is placed 30cm in front of a convex mirror of focal length 20cm. Find the size and position of the image formed by the convex mirror.

The focal length of a lens is +150mm. What kind of lens is it and what is its power?

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?

Draw a diagram to represent a convex mirror. On this diagram mark principal axis, principal focus F and the centre of curvature C if the focal length of convex mirror is 3cm.

An object lies at a distance of 2f from a concave lens of focal length f. Draw a ray-diagram to illustrate the image formation.

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?

What is the position of the image when an object is placed at a distance of 20cm from a concave mirror of focal length 20cm?