Water Droplet Microscope
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In this laboratory session, we will be using two water droplets to create a system similar to a microscope, which will allow us to magnify images. This builds on the concepts discussed in the water droplet magnifying glass experiment.
This page will give you some useful information about how the lab works, and what you will need to complete it.
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Once you have taken some pictures, you can try them with our image classifier activity towards the bottom of this page. If you get any great images, feel free to send us them in an email, we'd love to see them!
Watch and learn
This video describes the basic setup for the experiment and gives you some tips on how to carry it out.
What do I need to prepare?
Smartphone
Ideally a smartphone with a front camera, but a back camera can be used too.
Empty plastic bottle or clingfilm
These will be useful to protect your camera from getting wet.
Sample slides
Something interesting to take pictures of. If you don't have your own slides you can make your own as described at the end of this page.
Paper towels
These will be useful for mopping up any water spillages.
Torch
This will help to light the sample from below.
Roll of tape
We use a roll of tape to hold our slides over the torch. You can use anything else that's round and will hold the sample over your torch.
Tinfoil or black paper
This is to create a pinhole. If you don't have tinfoil you can use thick paper.
Pen
We use a hollowed-out pen to position our droplets. If you prefer you can use a drinking straw.
Water Bead Microscope Instructions
1. Protect your phone
Applying clingfilm helps the droplet to stick to your camera and also offers protection from water droplets. Most modern camera phones are water resistant, but it's better to be safe than sorry.
Try to make sure that the cling film is free from air pockets and crinkles for a better image.
2. Make a pinhole and place this on your torch
We use a pinhole to cut down on stray light that does not pass through the sample. This makes sure that our image will only contain our sample. We make this pinhole with a knife in tinfoil but you can use paper if you have no tinfoil.
3. Prepare your slides
If you have sample slides, place these over your torch. Here we have used a roll of tape to position them over the torch.
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If you do not have sample slides, you can create them using Sellotape:
Use a section of tape for the bottom of the slide
Place your sample over this tape
Stretch a final piece of tape over the top
In the image on the right we have created a sample slide from sugar.
4. Place a droplet over your sample
Placing a droplet of water on top of your sample will provide magnification.
We are using an empty pen in order to position the droplet. Take your pen and dip the end in the bowl of water so that a water droplet is captured in the hole of the pen. Lightly touch the end of the pen to the sample slide to create a small droplet over the area of sample you would like to magnify. Make sure that the light source is aligned with the drop.
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The image on the right shows a slide of a pine leaf positioned correctly above the torch.
5. Place a droplet on your phone camera
Using the pen, collect another droplet of water and deposit this on the camera. The goal here is to just cover the camera lens. Too big and the droplet will fall of when you turn the phone over, too small and the camera will try to focus beyond it.
6. Align the droplets
Stack some books at a height slightly greater than the tape (about 1cm). Place the phone on the stack of books with the camera hanging over the edge. Open the camera app and try to align the camera with the droplet on the sample. If done correctly, a circle containing the sample should appear on screen.
7. Capture some images
If you have done this correctly, you should be able to align the two droplets and achieve microscopic images.
The image on the right was taken using two water drops. The sample is a pine leaf.
How does this work?
How does a microscope work?
A microscope usually has two lenses which work together to create a magnified image.
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The lens located closest to the sample is called the objective lens. The objective lens collects light that passes through the sample, forcing the light to bend. The bending of the light makes the image appear larger.
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The second lens is called the eyepiece. This is the part of the microscope that you look into. Eyepieces further magnify the image and projects it onto the back of the eye so we can see it.
The water droplets act like a microscope
In this exercise we are making something that is similar to how a microscope works. The water droplet placed over the sample produces a magnified image of the sample.
This is then projected onto the water droplet positioned in front of the camera lens, which magnifies it further. The result is an image that is magnified.
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The magnification here depends on how much the far the light is refracted by the droplets. Droplets with higher surface curvature will cause the light to bend further. Similarly, materials with a higher refractive index will cause the light to bend to a higher degree. If you want to try and create a more magnified image, try and substitute the water (refractive index 1.33) with oil (refractive index 1.47) or sugary water (refractive index 1.5).
