Below are ideas for extending this topic beyond the activity & exploration you just completed.

• Lesson Assessment and Answer Key
• Activity: Students test their vision in the classroom.
• Readings: Three readings about vision and blindness.
• Discussion: Why does a lens make things appear upside-down?
• Discussion with Video: If the picture on the back of my eye is upside down, why don’t I see everything upside down?
  

These Common-Core-aligned readings are free with registration on ReadWorks. All readings include comprehension questions.

• The Human Body - Your Vision (Grade 3)
• Device May Help Blind People See (Grade 4)
• Louis Braille — A 12-year-old invented the system of raised dots that let people who are blind read (Grade 6)

Discussion

Why does a lens make an image appear upside-down?

The lenses in your eyes are known as “convex” lenses: they’re curved outward. As light rays enter the far edges of a convex lens, the light rays are bent inwards. In other words, light rays entering the top of the lens bend down toward the bottom of the retina, and light rays coming in from the bottom of the lens bend toward the top of the retina. This is why the image looks upside-down! (You might wonder: Why don’t we see everything upside-down? That is a question which puzzled scientists… learn more!

Discussion with Video

Why don't we see everything upside-down?

Light makes an upside-down picture on the retina of your model eye. The picture on the retina of your real eye is also upside down. So why don’t you see everything upside-down? Ask your students if they can think of an experiment that might answer this question.

Here's an experiment some scientists tried. They had someone wear eyeglasses that flipped the picture in their eyes so it was right-side-up. To find out what happened, watch this video.

It turns out that the answer is not in your eyes -- but in your brain. Your brain learns to make sense of the picture in your eyes -- whether it's right-side-up or upside-down.