RECTILINEAR PROPAGATION OF LIGHT
1.
Materials and tools (for 1 class = 30 students)
200
sheets of A3 newspaper (cut original size into two), 70 sheets of A4 plain paper,
35 toilet paper roll cores, 10 filtered water bags, 35 rubber bands, aluminum
foil (35 sheets of 12cm x 12cm foil), 30 pairs of scissors, some cutters or
razor blades, 15 rolls of adhesive tape, methyl alcohol, cotton gauze, some
pairs of compasses, and explanation sheets
2.
Preparation
1)
Cut A2 newspaper sheets into
A3 size sheets.
2)
Remove ink from filter water
bags using methyl alcohol and cotton gauze. Then cut the plain part of the bag
into 35 sheets of 5cm x 5cm plastic film. They will be used to make camera
screens.
3)
Reinforce weak toilet roll cores using white glue (polyvinyl acetate
glue).
3. Principle
Light rays from an object pass through a
small hole to form an image.
Since the light can only propagate straight, light rays
from upper parts of the object come downward after passing through the
pinhole and light rays from lower parts of the objects come upward. The inverted image on the screen shows
the light propagates rectilinearly.
LOW COST PINHOLE
CAMERA
Face the pinhole to the object and watch the image on the screen
through the opposite end.
Materials
and tools
Old newspapers, a toilet paper core,
a filtered water pack, aluminium foil or black paper, A4 papers, a rubber band,
a cutter or razor blade, a pair of scissors, adhesive tape, a pencil, a
ruler, and a compass
Method
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1. Cut the toilet paper core
into three short tubes.
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Two shorts tubes will be used to make inner tube and one short
tube will be used to make the outer tube.
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2. Cut the side of the two
short tubes like picture above.
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3. Two of them are cut. One must be left as it is.
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4. Overlap the open ends of the
tube paper and fix them with adhesive tape in order to make small diameter
tubes.
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5. Finished two small
diameter tubes.
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6. Open the filtered water
pack to make a plastic sheet.
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7. Draw a circle using a small
diameter tube on plain part of the sheet.
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8. Cut out the plastic bigger
than the circle and place it on an opening of one of the small diameter
tube.
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9. Fix the plastic sheet on
the tube using adhesive tape. This
plastic sheet becomes the screen of the camera.
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10. Overlap
three sheets of A3 size newspaper with 1cm gaps respectively.
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11. At the
other end of the newspaper connect a sheet of A4 plain paper using adhesive
tape.
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12. Using adhesive
tape, fix the small tubes on the edge of the newspaper like picture above.
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13. Roll up
the paper neatly. This long
tube becomes the inner tube of the camera.
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14. Fix the
inner tube with adhesive tape.
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15. Place another
three A3 size newspaper sheets and A4 plain paper. Fix them with adhesive tape. Then connect the last short tube on
an edge of the newspaper.
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16. Place
the inner tube near the original diameter tube. Then start rolling up the newspaper and
A4 paper around the tubes.
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17. After
you finish rolling up, fix the outer tube with adhesive tape.
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18 . Draw 12cm diameter circle
on a sheet of aluminium foil or black paper.
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19. Cut out
the circle and put it on the opening of the outer tube.
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20. Fix the
foil with a rubber band.
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21. Make a
hole on the foil using the compass needle.
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22. The
diameter of the hole is approximately 0.5mm.
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Finished pinhole camera
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