Reflection and refraction of light - CCEAThe position of an image in a plane mirror

• Draw a pencil line across the top of a sheet of white paper. Mark points A and B. Select a position for the object and label that O.
• Use a pencil and ruler to draw an incident ray from O to A and from O to B. Include arrows.
• Use a ray box to direct two rays of light along the lines from object O towards points A and B.
• Mark 2 pencil Xs to mark each of the reflected rays from A and from B.
• Remove the mirror and use a pencil and ruler to join the Xs These represent the reflected rays.
• Extend the reflected rays behind the mirror until they meet at point. This is where the image was formed. Label the point I. These dotted lines are called virtual rays.
• With a 30 cm ruler, measure the perpendicular distance from O to the mirror and from I to the mirror.
• Repeat the experiment for different positions of the object O.

Conclusion

For each position of the object:

• the perpendicular distance of the object O from the mirror equals the perpendicular distance of the image I from the mirror.

Another way of saying this is:

• the image is the same distance behind the mirror as the object is in front.