When light is reflected from a concave mirror, the image produced may be real or virtual - Leaving Cert Physics - Question 9 - 2022

To illustrate the formation of a magnified image in a concave mirror, draw the following rays:

1. A ray parallel to the principal axis reflecting through the focal point.
2. A ray passing through the focal point reflecting parallel to the principal axis.
3. These rays should intersect at a point beyond the mirror, indicating the position of the magnified real image.

A real image is produced when light rays converge at a point after reflecting from a surface. This image can be projected onto a screen, reflecting the actual position of the object.

To find the position of the real image, apply the mirror formula:

$\frac{1}{u} + \frac{1}{v} = \frac{1}{f}$

Given:

• Object distance (u) = -20 cm (negative as per sign convention)
• Focal length (f) = -12 cm

Substituting values:

$\frac{1}{-20} + \frac{1}{v} = \frac{1}{-12}$

This leads to:

$\frac{1}{v} = \frac{1}{-12} + \frac{1}{20}$

Solve for v to find the image distance.

Using the magnification formula:

$m = \frac{h'}{h} = \frac{v}{u}$

Where:

• h' = height of the image
• h = height of the object = 4 cm
• v = image distance (calculated previously)
• u = object distance = -20 cm

Substituting the values will yield the height of the image.

One practical use for a concave mirror is in shaving mirrors, which magnify the image of the face for a closer, clearer shave.

A convex mirror has a outwardly bulging surface. The side facing the object is the reflective side, allowing light to scatter and produce a virtual image.

A virtual image occurs when the light rays appear to diverge from a point behind the mirror. This image cannot be projected on a screen since the rays do not actually converge at that point.

Convex mirrors are commonly used as side-view mirrors in vehicles due to their ability to provide a wider field of view.