Making a Water Lens
This lesson developed by Reach
Recommended Age Group: Early Elementary, Later Elementary
What is a lens and how does it work?
A lens is a curved piece of clear glass or plastic used to
We can think about lenses by comparing facts about our eyes:
- Nearsighted people have eyes that are too long
from front to back.
- Farsighted people have eyes that are too short
from front to back.
- Convex lenses help eyes to focus up close.
- Concave lenses lessen the power of eyes so they can focus on things far
- Refraction is when a beam of light changes
- Convex lenses curve outward in the middle.
- Concave lenses curve inward in the middle.
- Observation skills
- Making inferences
- Drawing conclusions
- Clear plastic wrap
- Teaspoon or eyedropper
Students need table space and elbow room.
Procedures and Activity
- Ask, “What is a lens?”
Review concept of a lens being a clear piece of curved glass or
- What does a lens do?
A lens focuses a beam of light.
- Today, we are going to make a water lens and learn how lenses work.
- Lay a page of newspaper on desk or tabletop.
- Lay a piece of clear plastic wrap on top of newspaper.
- Put drop of water on plastic wrap.
- Observe the shape of the water drop.
- Look at how the newspaper print appears under the “water
- Why does the print appear the way it does?
- Add more drops of water. Note the shape of the water and how the
newspaper print appears.
- What is happening? How might this knowledge be useful?
- Talk about nearsightedness and farsightedness. Share information about
bifocals, where the top lens is for distance and the bottom lens is for
close-up and reading. Relate to water lens.
Closing - Original Question
Ask again, “What is a lens and how does it work?”
Is a water lens concave or convex? Review these terms and find a water
lens is convex—it curves out in the middle. A convex lens helps our
eyes to focus close up.
Have students share out loud what they have learned about lenses and
focusing light from doing this experiment.
Have students help other children do this experiment. Listen to them for
evidence that they understand the concept of a lens, the principles of
refraction, and the difference between concave and convex lenses.
- Invite an optometrist, ophthalmologist, or eyeglass fitter to come and
share more information about lenses, eyes, and glasses.
- Get some convex and concave lenses from a a toy store or science supply
shop. Experiment with looking at different objects with these lenses.
Write down what you see and why you think it happens.
- Think about the variety of uses of lenses—for studying insects,
making and using microscopes, helping eyes see, astronomy and
Careers Related to Lesson Topic
- Eye glass fitters
- Lens makers
- Eyes that are too short from front to back. This means that the person
can only read things from a distance.
- Bringing light waves to a point and helping something appear clearer
and sharper in detail
- Clear piece of plastic or glass that is curved to help focus beams of
- Eyes that are too long from front to back. This means that the person
can only read things that are up close.
- The change of direction of a beam of light
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