Magnifying Glass

a child's eye magnified

Build your own magnifying glass…

Do you know how a magnifying glass works? Did you ever think you could build your own? In the telescope project, there is a youtube video that shows you how to make a more complicated magnifying glass, but for this project, all you need is a bowl shaped piece of clear plastic, and a little bit of water!

For this project, you will need:

  • old plastic bottle
  • cup
  • marker
  • scissors
  • water


  • Place the base or rim of the cup on the upper portion of the plastic bottle
  • Use the pen to trace a circle
  • Carefully cut the circle out of the bottle. You should now have a curved lens in a bowl shape.
  • Hold the lens, rim up, and put a little water in it.
  • Hold it horizontally over your book or other object that you want to magnify, and look down through the water.

Try This:

  • Try making lenses of different sizes and depths (for example, using the deeper curves from the bottom of the bottle. Does this change anything?
  • Add more or less water. What happens?
  • Lift your magnifier up or drop it down over the object you’re examining. Does it get larger or smaller? Clearer or blurrier?

How it works…

When you add water to the curved shape you cut out of the bottle, you’re making a CONVEX lens; convex lenses are curved outward, thicker in the middle and thinner at the edges. The more water that pools in the centre of your home made convex lens, the thicker it will be. When light passes through water, it bends. This is called REFRACTION. The light refracts through the water in the convex lens, focusing and enlarging the objects on the other side.

Find the original project here.



a replica of a Newtonian telescope

Build a Newtonian telescope…

A telescope works by adjusting the focus of two lenses. The objective lens (the one at the end of the scope) needs to be convex (thin at the edges, thick in the middle) and the eyepiece lens (the one you look through) can either be convex or concave (thick at the edges, thin in the middle).

A telescope with two convex lenses is called a NEWTONIAN telescope, and the image you see through it will appear upside down.

A telescope with a convex objective lens and a concave eyepiece lens is called a GALLILEAN telescope. The image you see through this type of telescope will appear right side up.

If you have access to a concave lens, you can experiment with making a two piece Gallilean telescope, but unfortunately there is no way to MAKE a concave lens easily, as you can with a convex lens. You can, however, make a pinhole viewer in place of the eyepiece lens, and experiment with seeing the image inverted or right side up.

OPTION ONE – Two Biconvex Lenses

 For this project, you will need:

  • old plastic bottle
  • cup
  • marker
  • scissors
  • water
  • hot glue or superglue
  • optional: old pen or thick straw + 2 zip ties

To make a biconvex lens, follow the instructions in this youtube video:

  • Cut out two convex circles from the top of a plastic bottle
  • Glue the edges together, but leave a small opening
  • Dip the biconvex lens into a container of water and fill it as full as possible. Try not to leave any air inside, or you will get bubbles
  • Glue the rest of the lens together to seal the water inside
  • The tutorial is for a magnifying glass, so for this project, you can ignore the ends steps for building the frame, or you can continue and use the frame to hold the lenses

Make two of these lenses, and experiment with holding them at different distances from each other and from your eye. This is how you find the FOCAL POINT.

Begin by lining up the lenses in front of your eye. Close one eye and peer through the eyepiece lens, which you should hold very close to your open eye. Slowly move the objective lens farther away from the eyepiece lens, until a clear picture comes into view.

Try this:

  • When your image comes into focus, it’s upside down. Why do you think this effect is happening?
  • What happens when you look at something closer?
  • Experiment with lens sizes and depths. What do you notice about a wide, shallow lens vs. a smaller, deeper lens?

OPTION TWO – Biconvex Lens + Pinhole Viewer

You will need:

  • 1 biconvex lens
  • Aluminum pop can
  • Cardboard
  • Tape
  • Scissors
  • Pin
  • Sandpaper

To make a pinhole viewer:

  • Carefully cut a square out of the side of your pop can
  • Prick a hole in aluminum square with the pin. Try not to make the hole too big or too small (You may need to try a few times).
  • Use the sandpaper to smooth the rough edges of the pinhole. Make sure the pinhole is free from debris.
  • Cut a hole out of the centre of the cardboard.
  • Position the aluminum square so that the pinhole is over the cardboard hole. Keep it flat.
  • Tape the pop can square to the cardboard square, to prevent accidentally slicing your fingers.

Hold the pinhole viewer right to your eye and peer through it. Hold the convex lens right up to the pinhole and slowly move it away until things come into focus.

Try this:

  • Move the convex lens closer and farther away from your pinhole viewer and eye. What do you notice about the magnified image?
  • Is the image right side up or upside down? Can you change that by moving the lens?
  • What happens when you’re in a poorly lit room versus a bright, outdoor space?

How it works…

The pinhole viewer and eyepiece lens do the same thing; they are there to focus your eye. Light passing through a convex lens refracts inwards, coming together to a point a short distance from the lens. This is called the FOCAL POINT. Anything at this point will be enlarged and in focus, but objects past the focal range will appear upside down. With the pinhole viewer, only a little bit of light reaches your eye; you will notice that under lighting where you can usually see, the room appears dim. Using the pinhole telescope is more effective outdoors on a sunny day.

Find the original project here.


Inverted Image

the tools required to do the inverted image experiment
Project an image and flip it…

What happens when you project an image through a convex lens onto a wall? How about two convex lenses?

For this experiment, you will need:

  • Flashlight
  • Black construction paper
  • Scissors
  • Tape
  • 2 convex lenses


  • Cut out a circle of black construction paper that fits over the face of the flashlight
  • Cut an asymmetrical shape in the construction paper
  • Tape the construction paper to the front of the flashlight
  • Find a dark room and tape a large piece of black construction paper to the wall
  • Turn on the flashlight and shine the light at the black construction paper on the wall
  • Hold one convex lens between the light and the wall
  • Have a friend hold the other convex lens on the same path

Try this:

  • What do you notice about the light that hits the wall without any interference?
  • What do you notice when one lens interferes?
  • Try moving the lens closer and farther away from the light source. Does anything change?
  • What do you notice when both lenses interfere?
  • Experiment with the distance between the two lenses, the light source, and the wall.

How it works…

The asymmetrical image will be right side up when it’s projected onto the wall with no interference. This is light traveling in a straight line, being obscured by the black construction paper, but not bent. When you add a convex lens at the correct distance from the wall, the image should appear upside down. This is because the light traveling through the lens bends in on itself, and when it reaches the wall, it is inverted. If the lens is close to the wall, the image will appear right side up, but smaller. This is because the refracted light has not quite reached the focal point yet. If you add a second convex lens at the right distance, the inverted image will be re-inverted and appear right side up when the light meets the wall.

Find the original project here.