Images in a plane mirror
Stand a letter card in front of a mirror at different distances and find where its image is, how big it is and which way round it faces.
Core concept
A plane mirror forms an upright, same-size, laterally inverted virtual image as far behind the mirror as the object is in front
Topic: Light
When you look in a mirror, light from an object reflects off the mirror into your eyes. Your brain assumes light travels in straight lines, so you see the object as if it were behind the mirror. This image is virtual: the light does not really come from there, so it cannot be caught on a screen. In a plane mirror the image is upright, the same size as the object, the same distance behind the mirror as the object is in front of it, and reversed left to right (lateral inversion).
What you will learn
- Describe the image formed by a plane mirror.
- Show that the image is as far behind the mirror as the object is in front.
- Explain lateral inversion.
Before you start
- Know the law of reflection.
Materials
- Cards with the letters F, R and A
Equipment
- Plane mirror in a stand
- Ruler
Procedure
- Stand the letter F 5 cm, 15 cm and 25 cm from the mirror and record where the image is each time.
- Look at which way round the image of F faces.
- Try the letter A and the letter R.
How this simulation is simplified
- The mirror is flat and upright, and the card is 7 cm tall.