Key Points

The angle of incidence ($i$) is always equal to the angle of reflection ($r$). This is expressed as $\angle i = \angle r$. Both angles are measured with respect to the normal.

The incident ray, the reflected ray, and the normal to the reflecting surface at the point of incidence all lie in the same geometric plane.

When a light ray strikes a mirror perpendicular to its surface, the angle of incidence is $0^\circ$. The ray reflects back along the same path, making the angle of reflection also $0^\circ$.

A spherical mirror with a reflecting surface curved inwards. It is a converging mirror because it causes parallel rays of light to converge, or come together, at a point after reflection.

A spherical mirror with a reflecting surface that bulges outwards. It is a diverging mirror because it causes parallel rays of light to spread out, or diverge, after reflection.

The image can be enlarged or diminished, and erect or inverted, depending on the object's distance. For example, a dentist uses it to get a magnified, erect image of teeth when held close.

A convex mirror always forms an image that is erect (upright) and diminished (smaller than the object). This property allows it to provide a wider field of view, making it ideal for vehicle side-view mirrors.

A lens that is thicker at the center and thinner at the edges. It is a converging lens, meaning it bends parallel light rays passing through it to a single point.

A lens that is thinner at the center and thicker at the edges. It is a diverging lens, causing parallel light rays to spread out after passing through it.

Similar to a concave mirror, the image can be enlarged or diminished, erect or inverted. When used as a magnifying glass (object is close), it forms an enlarged and erect image.

A concave lens always forms an image that is erect and diminished in size, regardless of the distance of the object from the lens.

A real image is formed where light rays actually converge and can be projected onto a screen (e.g., image from a projector). A virtual image is formed where rays appear to diverge from and cannot be projected on a screen (e.g., image in a plane mirror).

The warning 'Objects in mirror are closer than they appear' is on convex mirrors because they form diminished images. The smaller image makes our brain perceive the object as being farther away than its actual distance.

In a plane mirror, the image is laterally inverted, meaning the left side of the object appears as the right side of the image and vice versa. This is also observed in spherical mirrors.