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Ingenium Canada Science and Technology Museum

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Broken Pencil Illusion

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Open 9 a.m. to 5 p.m., Tuesday to Sunday
Address
1867 St Laurent Blvd, Ottawa, ON
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Browse all Visitor Information for Canada Science and Technology Museum
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Broken Pencil Illusion

Broken Pencil Illusion
Download PDF version

Seeing isn’t always believing, especially when refraction is involved! See how water bends light, “breaking” a pencil right before your eyes.

What you need

  • Clear, round drinking glass
  • Pencil
  • Tap water

Make it

  1. Fill the drinking glass about two thirds of the way with water.
  2. Place the pencil inside the glass on an angle, so it’s resting on the rim.

Test it

Bend down until you are looking in line with the top of the water. It should look as though the pencil is broken in two!

Explain it

Light travels through different materials, or mediums, at different speeds. In this experiment, light first travels through the air – which is easy to move through – and then through the water, where it slows down. This change in speed causes the light to bend, or refract, meaning that the part of the pencil that is in the water will appear shifted.

Observe It

Many birds hunt by flying over the surface of water, then diving in once they see a fish. Like in this experiment, the image a bird sees of a fish isn’t where it really is; the image can actually be quite far from the real fish. The bird has to adjust where it dives in order to catch the fish. This effect is also caused by the refraction of light once it hits the water.

Go further

Draw an arrow on a piece of paper and hold it up behind the glass of water, about 30 cm from your eyes. What do you observe?

arrow

As if by magic, the arrow flips around!

The round outside of the glass forces the water into a rounded shape, which acts as a convex lens. This lens bends the incoming light towards the middle. Here, the light rays meet at what is called the focal point. Past the focal point, the image is inverted because the light rays overlap.

refraction diagram

materials for the broken pencil illusion
the broken pencil illusion

Program Details

SCITECH
Canada Science and Technology Museum
Duration
10 minutes
Difficulty Level:
Easy
Program Location
Online
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  • View other programs related to Sciences, Education

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About Canada Science and Technology Museum

Canada Science and Technology Museum
The Canada Science and Technology Museum tells Canada's innovation story in an immersive, educational, and fun way.
Read more about the museum

Contact Us

Canada Science and Technology Museum
1867 St Laurent Blvd
Ottawa ON K1G 5A3
Canada

613-991-3044
1-866-442-4416
contact@IngeniumCanada.org
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  • Plan Your Visit
    • Health and Safety
    • Hours
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    • Accessibility
    • Browse All Visitor Information
    • Buy Tickets
    • Online Resources for Science at Home
    • About the Museum
  • What's On at the Museum
    • Events
    • Exhibitions
    • Spaces and Studios
  • Bookings and Rentals
    • School Programs
    • Birthday Parties
    • Summer Camps
    • Venue Rentals
    • Travelling Exhibitions
    • Virtual Field Trips
    • Group Visits
  • Educational Programs
    • School Programs
    • Virtual Field Trips
    • Program Location
      • At the Museum
      • At Your School
      • Online
      • Browse all Educational Programs
    • Popular Links
      • 3D Educational Resources
      • Digital Learning Kits
      • Games and Apps
      • Online Resources for Science at Home
      • Tell Me About
      • Try This Out
  • Collection and Research
    • Research Institute
    • Research Projects
    • Collection Resources
      • Ingenium Collection
      • Collection Highlights
      • Conservation and Collection Services
    • Library and Archives
      • Library and Archives Services
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    • Open Access
      • Ingenium APIs
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      • Open Documents
  • Projects and Initiatives
    • Ingenium Channel
    • Curiosity on Stage
    • Women in STEM
    • Innovation Storybook
    • Species at Risk in Canada
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