Light Exhibit: Afterimage

Autumn and Kali


Turn on the flashlight and shine it through the hole. Stare at it for 20 seconds, then look at the wall. Notice the image you see.

How It Works

Light entering your eye changes the chemicals in the retina. Looking at the light for that long desensitizes the retina. When you look at the blank wall, light shines onto your retina, the desensitized spot on your retina doesn’t respond as well to the new light, making you see a negative afterimage of the shape.

Vocabulary and Application

  • Type of wave

    • Definition: Light is the infrared, visible, and ultraviolet rays. (Between x-rays and microwaves)

    • Project Demonstration: It demonstrates how the retina is affected by the visible light with concentrated light waves.

  • Wavelength

    • Definition: The distance between each crest of a wave; color, different wave lengths make different colors

    • Project Demonstration: after looking at the light, your eye determines the wavelength by showing a certain color of the afterimage because wavelength determines color

  • Frequency

    • Definition: The number of waves passing a point in a certain amount of time; wavelength/second

    • Project Demonstration: same as wavelength

  • Amplitude

    • Definition: The distance from the rest position of a wave to the crest; intensity of brightness

    • Project Demonstration: Your eye is chemically changing because of the high amount of light the flashlight gives off. If the flashlight were dim, it wouldn’t be able to give such an intense effect as where the bright flashlight works better.

Our Concept: How We See

Light passes through the cornea, and then through the pupil, with the iris controls the size of the pupil, then the light goes through the lens which focuses the light onto the retina. The cells on the retina convert the light into electric signals which are sent to your brain.

This applies to our project because the bright light is hitting your retina for so long, it becomes desensitized. Then when you see the new light your desensitized retina can’t see it as well. creating a negative dark spot.