Periscope

http://www.exploratorium.edu/science_explorer/periscope.html

Materials

  • Two milk cartons
  • Two small mirrors
  • Razor blade
  • Ruler
  • Tape

Activity (20min)

  1. Remove the roof of the milk cartoon (yes, the roof is the top triangular portion)
  2. Cut a square hole in the bottom of the milk cartoon
  3. Lie the cartoon on the side, and use a ruler and pencil to draw a 45o line at the bottom of the carton. Do this for both sides
  4. Could ask the kids to figure out how to make a 45o line
  5. Cut out a thin slit along this line
  1. Stretch masking tape between the two slits, sticky side up
  2. Mount the back side of the mirror to the masking tape
  3. Look through the window and verify that you see the reflection of the ceiling
  4. Repeat steps 1-8 for second milk carton
  5. Slide the two milk cartons together, and tape together

Lenses

http://www.exploratorium.edu/science_explorer/pictures_from_light.html

Materials

  • Lenses with varying magnification
  • Flashlights
  • Paper
  • Gloves, for handling optics (kids will have fun putting them on, acting very professional…)

Activity – Imaging using Lenses (15min)

1) Break into groups, and discuss how lenses work. Introduce the concept of focal length; each lens has a focal length depending on the shape. Shorter focal length can lead to larger magnification…ect.

2) Referring to lesson on pinhole cameras, tell them that you can also make images using lenses. These images will also be upside down.

a) Most cameras actually use both lenses and tiny pinholes to make really nice pictures.

3) Give each of the kids a piece of paper and have them cut a weird shape out of the middle.

4) Have each of the kids don gloves for use in handling the lenses. Tell them when scientists work with lenses it is very important to keep them clean and free of finger prints. They will probably feel very professional and scientific

5) Take another piece of paper to use for the screen, and try and image their shapes illuminated by the flashlight onto the screen, as demonstrated in the picture below

a) Ideal setup would have source 2*focal length in front of the lens, and screen 2*focal length behind the lens

b) Can determine focal length by imaging lights from ceiling onto the ground, assume ceiling lights are at infinity, and focal length is distance between lens and ground.

6) Try playing around with the distance between lens, source, and image

Telescopes

Materials

  • Same as above
  • Plastic/cardboard toilet paper rolls to mount lenses in
  • Construction paper to extend telescope length
  • Tape, razors, or something to mount lenses into tubes

Activity – Making Telescopes (20min)

1) We can play more tricks with lenses that we can with pinholes.

  1. If we use two or three lenses we can flip the images back over (we won’t try to do this, its kind of tricky I think…)
  2. You can also magnify the images you are looking at. This is how telescopes and microscopes work

2) Have two of the students help mount two lenses of different focal lengths into the end of separate tubes

  1. Determine focal length (roughly) using method above, or if it is written on the lens take note of it
  2. Magnification will be ratio of focal lengths (M=fobj/feye), so use the lens with longer focal length for the object side (away from eye)
  3. Optimal distance between lenses will be the sum of the focal length (d=fobj+feye), so make sure the tubes are long enough

3) Take a roll of construction paper and cut it down to roughly the length determined previously (d=fobj+feye)

4) Tape on one tube/lens unit to the end

5) Slide the other tube/lens unit in and adjust the length to obtain a clear image, tape it in place

6) Cross your fingers and hope it works!