What it shows
A water drop or a clear gel bead stuck on a phone camera lens turns the phone into a microscope, enough to photograph stomata on a leaf peel and tiny organisms in pond water. It shows the pores that let a leaf breathe and the unseen life of a pond.
The science
A small drop of water or a transparent bead in front of the lens bends the light strongly and increases the magnification greatly, so the phone sees a tiny object as large. A leaf’s lower surface has pores called stomata surrounded by two guard cells, which open to let in carbon dioxide and release oxygen and water vapour. Pond water holds single-celled organisms such as Paramecium and Euglena and tiny algae that move or float and are invisible to the naked eye.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A smartphone with a camera
- A small clear drop of water or a bead of clear glue held in a punched card ring
- A thin card with a 3 mm hole
- Clear nail polish, if available, for a leaf impression
- Clear sticky tape
- A glass slide or a clear plastic slip
- A jar of pond water with some green scum
Safety
For this project: Wash your hands after touching pond water and do not drink or taste it. An adult must supervise near ponds and use only the shallow edge. Do not use the nail polish in a closed room.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Fix the card with the 3 mm hole over the phone’s camera lens with a little tape, so that the hole sits exactly over the lens.
Place a small drop of clean water in the hole using a pin. The drop must sit in the hole without spilling on the lens.
Switch on the camera and zoom a little. Place a printed page near the lens to see the letters enlarge, and adjust the drop and the distance until it is sharp.
Paint a thin layer of clear nail polish on the underside of a leaf of a spider lily or money plant, let it dry, peel it with clear tape and stick it on a slide.
Hold the phone with the drop over the peel, lit from below by a window or torch, and take photos of the kidney-shaped guard cells.
Put a drop of pond water on a clean slide and look at it the same way. Watch for moving specks and note their shapes.
Count the stomata in one field of view for three leaves and compare the upper and lower surface counts.
Print your best photographs, label the stomata and the pond organisms, and write what you found with the approximate size of each.
What you should see
The leaf peel shows paired guard cells around tiny pores, many more on the lower surface than the upper, and the pond water drop shows green single-celled algae and moving specks.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What are stomata and what is their job?
Tiny pores in a leaf that allow gas exchange and release water vapour.
2Why are more stomata on the lower surface?
There the leaf is shaded and cooler, so less water is lost.
3Why does a drop act as a lens?
Its curved surface bends light inward like a convex lens.
4Why is the pond water kept covered after the test?
Open water collects mosquito eggs and dust, and the sample is not safe to touch for long.
Take it further
Measure the stomata density on leaves in sunny and shady places and compare the average count per field.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
Science projects
Biology Models Guide
Make the heart, lungs, kidney, eye, cell and more, and explain them well
Science projects
Science Projects for Class 9 and 10
Models and experiments for high-school physics, chemistry and biology