Image Viewer
See what the eye sees!
Pinhole or lens
Topics: Light, Optics,
Refraction
Materials List
 Convex lens, 10 cm
focal length, 38 mm
(1½”) diameter
 Tube, 38mm (1½”),
by 15 cm (6”) long
 Opaque file folder
or cardstock
 Foil squares, 8 cm
(3”) sides
 Wax paper, 8 cm
(3”) sides
 Tape and/or labels
 Portion cup and lid,
¾ oz. size
 Hole cutting tool
 Pushpin, pin or
round toothpick
This activity can be used
to teach:
 Light reflecting from
objects and entering
the eye allows (Next
Generation Science
Standards: Grade 4,
Physical Science 4-2)
 Waves are reflected,
absorbed, or
transmitted (Next
Generation Science
Standards: Middle
School, Physical
Science 4-2)
 Science &
Engineering Practices
(Next Generation
Science Standards:
Grades 3-12)
Tape/label collar
Do not point at
the Sun!
Light blocking
tube
Cardboard tube with wax paper
covering the other opening
Explore images formed by a pinhole and a lens. See what the eye really “sees” – an
inverted image!
Assembly
1. Cover one end of a 38 mm (1½”) diameter cardboard tube with an 8 cm x 8 cm
(3” x 3”) square of wax paper or other translucent material. Pull the wax paper
down around the sides of the tube and secure the wax paper to the tube with tape
or labels. The wax paper should be as flat as possible over the end of the tube.
2. Wrap a 19 x 20 cm (7½” x 8”) or so section of thin, opaque (green, etc.) file
folder or cardstock around the cardboard tube. Roll so the darkest side will be on
the inside. Secure the long edge with tape or a label. Alternately use a 2nd opaque
cardboard tube that has a slightly larger diameter and thus a “telescoping” fit.
3. Print the warning “Do not point at the Sun!” on the side of the tube.
4. Pull the open end of the inner tube ¾th of the way out of the outer tube. If the
outer tube opening is too small to allow this movement then push the inner tube
back in and pull out from the other end. Reinsert the inner tube with the wax
paper end going in first into the outer tube. The result, one way or the other,
should be a smoother “telescoping” fit of the two tubes.
5. Cover the open end of the outer tube with an 8 cm (3”) square of foil. Pull the foil
edges down around the sides of the tube and secure with a small piece of tape or a
label. The foil needs to be easily removable.
6. Make a pinhole in the center of the foil with a pushpin, pin or round toothpick.
Have several foil squares available so different sized pinholes can be investigated.
Mounting the convex lens: (Caution! Glass lenses can break!)
7. Cut or punch a 2.5 cm (1”) diameter hole in the center of a ¾ oz. portion cup and
lid.
8. Place the lid, upside down, on a flat surface.
9. Unwrap the 38 mm (1½”) diameter convex lens. Pick up the lens by touching
only the edges of the lens. Clean the lens, if needed.
10. Place the lens in the center of the upside down lid. Place the portion cup, regular
opening downward, over the lens/lid. Gently push down on the cup bottom,
going around, until the cup snaps into the lid, as shown below. Later this lens
will be mounted in the outer tube, in place of the foil (see the To Do and Notice
on the back of this page).
Designed and written by Michael Pollock (RAFT)
Push around on bottom
1st 2nd (etc.)
Copyright 2015, RAFT
To Do and Notice
An eye that has been in a lighted setting needs time to adjust to the dark. The time needed to see dim images is
reduced if the eye is closed or the room lighting reduced, for awhile, before using the pinhole viewer. The
pinhole’s images will be very dim as most of the available light is blocked from entering by the foil.
1. In a darkened room point the pinhole opening of the image viewer at a brightly lit distant view (or overhead
projector image). A view with sky and trees (or buildings) makes the orientation of the image more
noticeable. Look in the image viewer by placing the open end up to an eye. Slide the tubes in and out. How
does the image look and how does the image change as the tubes are moved in and out?
2. What difference does having a larger or smaller pinhole make in the image seen on the wax paper screen?
3. Look at moving cars or people in the same way as step 1. Which direction are the cars or people moving?
4. Look at a brightly lit area about 1 m (3 ft) away. Slide the tubes in and out. How does the image change?
5. Replace the foil with the lens/portion cup combination. Use tape to secure the lens to the tube as needed.
Repeat steps 1 to 4. How are the images, formed by a lens, different from those formed by a pinhole?
The Science Behind the Activity (Simplified light ray diagrams are not to scale)
A pinhole can form a focused image because the material around the pinhole blocks the light rays that would
create a blurry image. The image will be relatively dim because only a little of the light emitted by or reflected
from the object can enter the pinhole. A larger pinhole will permit more light to enter creating a brighter but
blurrier image. The larger the pinhole the blurrier will be the image.
Inverted image
Translucent screen
The images on the translucent screen will grow larger as the screen is moved farther from the pinhole or smaller
if moved closer. A pinhole can form a focused, inverted image over a range of distances from the pinhole.
Images are in focus when the
screen is moved closer or
farther away
Replacing the pinhole with a lens will allow much more light to enter. However the lens will form a focused,
inverted image at only one distance, based on the lens’s focal length and the distance to the object.
Focal length
Focused image is formed at a
set distance from the lens, as
determined by the lens’s focal
length and distance to the
object
SAFETY NOTE: Convex lenses converge and concentrate light rays. Pointing a lens or viewer toward the Sun
could cause eye damage! The Sun’s rays could also be accidentally focused into a hot spot and cause a fire.
Taking it Further
The image viewer can also be used to model near and far sightedness, see the RAFT idea sheet Modeling Near and
Far Sightedness. Make a pinhole camera. Research and create a camera obscura room.
Web Resources (Visit www.raft.net/raft-idea?isid=168 for more resources!)


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Ray Diagrams for Lenses http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/raydiag.html
Anatomy of a Lens - http://www.physicsclassroom.com/class/refrn/Lesson-5/The-Anatomy-of-a-Lens
Camera Obscura information - http://brightbytes.com/cosite/what.html
Image Viewer, page 2
Copyright 2015, RAFT