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Reflections

Have you ever noticed that the way you look in photographs is different from the way you look in the mirror? That’s because a photograph is a true image, while your reflection is a mirror image. 

This activity gets students exploring their own reflections and thinking about how they can see themselves. 

When light from an object hits a flat, shiny surface, nearly all of it is reflected (bounces back) in a predictable way. The light bounces back at the same angle it came in at. When your eye catches the light, it appears as though it came from behind the mirror. 

When you look in a flat mirror, you see a reflection of yourself that is the same size as you but reversed.

Right and left are reversed in the image because a light ray coming off your right hand bounces off the mirror, and into your eye. To your eye and brain, the light ray appears to have come from the left hand of someone who looks just like you, standing on the other side of the mirror. Because the image is “behind” the mirror, your right hand is their left one. 

Ponder this: we may describe a reflected image as “switched from side to side”. But really, a mirror only changes the direction the object is facing into and out of the mirror. That is, back to front or front to back . 

Objectives

  • Explain properties of visible light.

  • Describe how light rays can change direction.

  • Demonstrate how visible light is reflected.

Materials

  • Per Student:
    flat (plane) mirror
    students’ faces and hands
    desk or classroom object (pen, eraser, ball ect.)
    *optional: mirror position template
    *optional: Overhead transparencies or Mira plastic mirrors

Key Questions

  • Can you explain why you can see your reflection in a mirror?
  • Touch one ear. Which ear are you touching? Which ear is your reflection touching?
  • Is there anything special about your face that is only on one side (a freckle or a mole)? Which side is it on in your reflection?
  • What would happen if the mirror had a bumpy surface?
  • What would happen if the mirror had a dull surface?
  • Can you think of any other objects that can act as a mirror (spoons, puddles, windows. etc.)? What are differences between a regular mirror and those objects? What are the differences you see in the images reflected in those surfaces?

What To Do

  1. Hand each student a mirror and ask them what mirrors do. Encourage them to describe their understanding of how mirrors work and what they show.
  2. Use questions to prompt students to explore their own reflections. How do their reflections compare to reality? On which side do they part their hair, on which side to they have a freckle or other noticeable feature? When they touch an ear, which ear are they touching, and which is their reflection touching?
  3. Discuss with students whether their image is an exact copy of themselves. If not, how do their reflections differ?
  4. Based on their observations, have students make predictions of how various classroom objects (a map, a ball, a clock, a book, a ruler, etc.) will look in a mirror, and then test to see if their predictions are true. What objects will look exactly the same? Which objects will look different, and how?

Optional:

  1. To get a real understanding of how exactly the mirror image is different, try using an overhead transparency or a Mira plastic mirror and a copy of this drawing. (Just like when you see your reflection in a glass window pane, these tools allow you to see a reflection and see through the “mirror” at the same time.) Hold the transparency or Mira mirror upright on the line and look “into” it to see the reflection. The reflection will appear to be on the page to the right of the line.
  2. With your pencil behind the transparency, trace the reflection you see onto the paper. Measure the distance between the original stick figure and the mirror; then measure the distance between the reflected stick figure and the mirror. (They should be exactly the same distance)
  3. Make a list of at least ten things that reflect images (spoons, puddles, windows, etc.). What is different about the way our reflections appear in those surfaces?

Extensions

  • Ask students where mirrors are and what they’re used for. Examples: in the bathroom for looking at oneself, at the dentist’s for seeing in hard-to-reach places, in the car for viewing surroundings, and so on.