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Body Lab 3-5 / Week 08 / Body Lab Day
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Week 08 · Eyes and Seeing

Body Lab Day

Body Lab Day: Pupil Watch
// How light becomes a picture
⏱ about 15 min

Body Lab Day: Pupil Watch

Rocket and Raven sit by a mirror in a dim room. Their pupils look big and dark.

"Watch closely," Raven says. "What do you notice when the lamp comes on?"

A grown-up switches on the lamp. Rocket stares. "My pupils shrank!"

Nova hums. "Now guess why the iris would do that," she says.

  1. We see things when reflected light enters our eyes.
  2. The iris controls how much light goes through the pupil.
  3. The lens changes shape to focus light on the retina.
  4. Rods help in dim light. Cones sense color.
  5. The optic nerve carries signals to the brain, which makes the picture.
◇ PUPIL WATCH
Sit with a partner in a room with the lights low for about one minute.
Look at each other's eyes, or use a mirror. Notice the size of the pupils.
A grown-up turns on a ceiling light or a lamp.
Watch the pupils right away. What happens to their size?
Turn the light low again. Wait and watch.
On paper, draw an eye in dim light and an eye in bright light.
Safety first
Never shine a flashlight or lamp straight into anyone's eyes.
Never look at the Sun.
Look only. Do not touch eyes.
Joining in is a choice. Anyone can be the light switcher instead.
For a grown-up
Keep the light normal room light, aimed away from faces.
Ask: what did you notice? Why might pupils get smaller in bright light?
BODY LAB CHECK
  • Read the question.
  • Tap your answer.
What happened to the pupils when the light came on?
What happens to pupils when the light goes low?
Which colored part of the eye changes the size of the pupil?
WHY THIS EXERCISEThe iris muscles change the pupil's size to control the light.

Brilliant observing! Next week we switch senses and explore ears, hearing and balance.

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