Focus Pocus #42

(grades 5-10)
Soft-bound, 64 page book, 20 reproducible activity sheets, full teaching notes.

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Make a canning-ring projector, a washer-lens reducer, a beverage-bottle magnifier, a soda-straw microscope, a lens platform to trace the path of refracting light rays, even a working mechanical eye that probes the mystery of nearsighted and farsighted vision. Explore angular size and graph visual acuity. Discover the inverse relationship between actual distance and apparent size.

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Table of Contents for #42 Focus Pocus:

Preparation and Support

A TOPS Teaching Model • Getting Ready • Gathering Materials • Sequencing Activities • Gaining a Whole Perspective • Review/Test Questions

Activities and Lesson Notes

  1. 1. Pin Rays
  2. 2. Light Wagon
  3. 3. Lens Platform
  4. 4. Itsy-Bitsy Lenses
  5. 5. Spotlight
  6. 6. Elevator Up
  7. 7. Variable Lens
  8. 8. Pinhole Projector
  9. 9. Canned Eyeball
  10. 10. Eye See
  11. 11. Spare Change
  12. 12. Money Math
  13. 13. Near Point
  14. 14. Water Magnifier
  15. 15. It's a Microscope!
  16. 16. Suspenders
  17. 17. Drawing Pin
  18. 18. In Print
  19. 19. Jabberlooky
  20. 20. Higher Powers

Supplementary Pages

pin rays • light wagon • lens platform • bottle ruler • vision graph • money ruler • 100 word box • eye patch • powers ruler • eyepiece • millimeter grid • stage • black/white octagon • double eyepiece


Complete Master List for #42 Focus Pocus:

Key: (1st/2nd/3rd) denote needed quantities: (1st) enough for 1 student doing all activities; (2nd) enough for 30 students working in self-paced pairs; (3rd) enough for 30 students working in pairs on the same lesson. Starred* items may be purchased below.

  1. 1/15/15: scissors
  2. * 4/60/60: microscope slides
  3. * 0.1/1/1: cups modeling clay
  4. * 6/90/90: straight pins, about 1 inch long
  5. * 1/5/5: rolls 1/2 inch clear tape
  6. 1/5/15: metric rulers
  7. 1/8/15: sets assorted coins: 4 pennies, 1 nickel, 1 dime, 1 quarter
  8. * 3/45/45: straight plastic drinking straws
  9. * 1/5/5: rolls 3/4 inch masking tape
  10. * 2/30/30: TOPS hand lenses or equivalent

  11. 2/30/30: glass bottles, soda or beer, about 20 cm tall
  12. 1/15/15: index cards
  13. * 1/15/15: regular canning rings, not wide-mouth
  14. 1/1/1: roll plastic wrap
  15. * 1/15/15: heavy rubber bands
  16. * 1/15/15: dropper bottles
  17. * 1/15/15: metal washers with 5/16 inch (8 mm) hole
  18. 1/1/1: box facial tissue, or roll toilet paper
  19. * 4/60/60: paper clips
  20. * 2/30/30: wooden clothespins

  21. * 1/3/15: hand mirrors
  22. 1/15/15: empty cans, 2 7/8 inches in diameter by 4 3/8 inches tall; a common size for vegetables with 14.5 to 15.5 ounce net weights. A regular-size canning ring must nest inside without falling through. Choose cans that can be opened from both ends.
  23. 1/1/1: roll waxed paper
  24. * 1/1/1: roll aluminum foil
  25. * 1/5/15: candles with drip catchers
  26. 1/2/5: packages matches
  27. 1/10/15: meter sticks
  28. * 1/1/1: roll adding machine tape
  29. 1/1/1: pencil sharpener
  30. 1/8/15: hand calculators (optional)

  31. * 1/5/15: 1/16 inch diameter finishing nail
  32. * 3/15/45: 1 1/2 inch nails
  33. * 1/5/15: 2 1/2 inch nail
  34. * 1/5/15: 3 1/2 inch nail
  35. 1/15/15: palm-sized pieces, clear, flat plastic from bakery "clamshell" cartons
  36. 1/2/5: hole punch
  37. 1/1/1: jar petroleum jelly
  38. 1/1/1: packages each: granulated sugar, table salt, pepper, whole poppy seeds
  39. * 1/1/1: bottle glycerin (optional)
  40. 1/3/15: dark crayons or marking pen
  41. various: samples printed matter: newsprint, 4-color magazine ads, computer printouts

  42. 1/15/15: wooden toothpicks

Convenient Shopping:

Adding Machine Tape

2-1/4 inch x 100 feet

Adding machine tape.

Aluminum Foil

regular strength, 20 square feet x 12 inches rolls

Buy aluminum foil here as a convenience item, or for less in many grocery stores.

Candles - emergency

cylindrical, 5 inches by about 3/4 inches diameter

Also called utility candles. A handy heating source. Correctly sized for #09 Floating and Sinking. Drip catchers not included.

Canning Rings with Lids

fit regular-mouth canning jars

These may be available only seasonally in some stores. Avoid wide-mouth size. Needed for #16 Pressure and #17 Light. Only rings (not lids) are used in #40 Earth, Moon & Sun, and #43 Focus Pocus.

Clay - modeling

oil-based, non-drying

Sold by the 100 gram stick, about 1/4 cup, in assorted colors (our choice). One stick serves a whole classroom for TOPS applications.


wooden, spring-action

These are handy lab items to keep in stock. We use them as bulb holders, tongs, clips, and more.

Dropper Bottle with Eyedropper

1/2 ounce, amber glass

Very handy for storing and conveniently dispensing small quantities of liquid. You may also purchase eyedroppers without bottles as item #1120.


liquid dispensed in 2 fl. oz. plastic bottle

Used in #13 Cohesion/Adhesion and optionally in #42 Focus Pocus. A great addition to soap solution for making strong, large bubbles.

Magnifier - hand lens

3X clear plastic hand lens

You'll find many uses for this basic tool of scientific inquiry. Very nice quality for the price. Supports #17 Light, #23 Rocks and Minerals, and #42 Focus Pocus. (One 3X hand lens is also included in each #100 Triple Magnifier Kit.)

Microscope Slides

glass, standard size

Used in #17 Light for diffraction experiments. For viewing microscope specimens, consider cutting slides, almost for free, from clear plastic bakery cartons. Smooth any sharp edges with sandpaper or an emery board.


4x6 inch clear, reflecting plastic

A handy scientific tool. It is made of shatter-proof plastic with peel-off protective film. The plane surface may be flexed for funny faces and interesting experiments. Needed in #17 Light, #42 Focus Pocus.

Nails - 2 1/2 inch

steel carpenter's flat-head nail, 10-penny

Used in some TOPS titles. A surprisingly handy scientific supply.

Nails - 3 1/2 inch

steel carpenter's flat-head nail, 16-penny

A specialty item supporting #42 Focus Pocus and #20 Magnetism.

Nails - 1 1/2 inch

steel carpenter's flat-head nail, 6-penny

A specialty item supporting #42 Focus Pocus.

Nails - wire

1/16 inch diameter steel

A specialty item supporting #42 Focus Pocus. Many small light nails, including finishing nails, have this approximate diameter.

Paper Clips

size #1, steel, box of 100

Paper clips have 1001 uses in TOPS experiments, and science in general. Feel free to use paper clips you already have, but be aware that different brands come in different sizes and weights. In experiments where uniformity is important, don't mix brands.

Rubber Bands - assorted

10 grams each of thin, medium and thick

You get 30 grams of soft, strong, durable rubber bands: thin #16 (about 50), medium #32 (about 20), and heavy-duty #64 (about 10). These sizes are specifically selected to work in most TOPS experiments.

Straight Pins

steel, one and 1/16 inch long

Used in many TOPS experiments. Sometimes required for their magnetic properties. Don't purchase aluminum straight pins by mistake.

Straws - straight

plastic, thin

Any length straw, between 0.20 and 0.25 inches in diameter is suitable. Grocery stores generally carry straws with flexible "elbows." You can use those if you cut off the bendable section before using.

Tape - clear

3/4 inch x 1000 inch roll

Your standard desk tape with matte write-on surface.

Tape - masking

3/4 inch x 55 yd roll

A handy science supply used in most TOPS modules.

Washers - small

7/8 inch flat washer with 3/8 inch hole

Used in many TOPS labs. Item #1290 (medium tubing) used in #16 Pressure fits through these smaller washers.

Teaching Tips for #42 Focus Pocus:

We encourage improvisation - it's one of the main goals of our hands-on approach! You and your students might invent a simpler, sturdier or more accurate system; might ask a better question; might design a better extension. Hooray for ingenuity! When this occurs, we'd love to hear about it and share it with other educators. Please send ideas and photos to

Lesson by Lesson Objectives for #42 Focus Pocus:

  1. Lesson 1: To track the path of light as it refracts through glass. To recognize that light bends more sharply as its angle of incidence increases.
  2. Lesson 2: To develop a model that demonstrates the direction light refracts as it passes from air to glass to air.
  3. Lesson 3: To understand why light rays bend inward when refracted through a convex lens. To focus light rays from a distant landscape as an inverted image on an index card screen.
  4. Lesson 4: To explore the relationship between the size of a water-drop lens and its focal length. To practice drawing accurate diagrams based on real measurements.
  5. Lesson 5: To vary the shape of a water lens from highly positive to highly negative curvatures. To examine how each lens shape refracts parallel light.
  6. Lesson 6: To study how the focal length of a convex lens varies with curvature. To understand why neutral and concave lenses do not project a focused image.
  7. Lesson 7: To study how different lens shapes magnify or reduce images. To interpret light ray diagrams.
  8. Lesson 8: To understand how pinholes focus light. To compare the properties of pinholes and lenses.
  9. Lesson 9: To construct an artificial eye, and determine whether it is farsighted or nearsighted. To understand how the human eye accommodates to both far and near vision.
  10. Lesson 10: To plot personal visual acuity as a function of distance. To discover the near limit of your eye's ability to accommodate.
  11. Lesson 11: To measure the apparent size of coins as subtended angles in your field of view. To observe how the apparent size of an object increases as its distance to your eye decreases.
  12. Lesson 12: To explore the inverse relationship between the distance of an object from your eye and the angle it subtends in your field of view. To appreciate the power of mathematics as a predictive tool.
  13. Lesson 13: To study the inverse relationship between the scale of an object and its distance from your eye. To evaluate the power of a hand lens.
  14. Lesson 14: To build a water magnifier and learn how to use it. To develop creative writing and drawing skills.
  15. Lesson 15: To build a microscope and learn how to use it. To investigate how the properties of a plano-convex lens change with size.
  16. Lesson 16: To investigate the optical properties of a "suspender lens" microscope. To describe and draw common kitchen spices at 25X magnification.
  17. Lesson 17: To accurately draw a pin 25X larger than actual size by measuring it under a microscope. To reduce this enlarged picture to actual size by observing it at a distance.
  18. Lesson 18: To examine printed type with a microscope. To understand how dotted "halftones" combine to produce all shades of grey plus a spectrum of color.
  19. Lesson 19: To use the pinhole like a magnifying lens. To compare the images produced by pinholes of various size.
  20. Lesson 20: To construct and use a van Leeuwenhoek microscope with tiny water lenses that magnify from, 60X to 100X. To begin an exploration of the world of small.

National Science Education Standards (NRC 1996) for #42 Focus Pocus:

TEACHING Standards

These 20 Activity Sheets promote excellence in science teaching by these NSES criteria:
Teachers of science...
A: ...plan an inquiry-based science program. (p. 30)
B: and facilitate learning. (p. 32)
C: ...engage in ongoing assessment of their teaching and of student learning. (p. 37)
D: and manage learning environments that provide students with the time, space, and resources needed for learning science. (p. 43)

CONTENT Standards

These 20 Activity Sheets contain fundamental content as defined by these NSES guidelines (p. 109).
• Represent a central event or phenomenon in the natural world.
• Represent a central scientific idea and organizing principle.
• Have rich explanatory power.
• Guide fruitful investigations.
• Apply to situations and contexts common to everyday experiences.
• Can be linked to meaningful learning experiences.
• Are developmentally appropriate for students at the grade level specified.

Unifying Concepts and Processes

NSES Framework: Systems, order, and organization • Evidence, models and explanation • Constancy, change, and measurement • Form and function
Core Concepts/Processes: Water drops are shaped like convex lenses. • Small water drops are powerful magnifiers with short focal lengths.

Science as Inquiry (content standard A)

NSES Framework: Identify questions that can be answered through scientific investigations. • Design and conduct a scientific investigation. • Use appropriate tools and techniques to gather, analyze, and interpret data. • Develop descriptions, explanations, predictions, and models using evidence. • Think critically and logically to connect evidence and explanations. • Communicate scientific procedures and explanations. • Use mathematics in all aspects of scientific inquiry.
Core Inquiries: Inquire into the nature of light refraction and image magnification with water drops.

Physical Science (content standard B)

NSES Framework: Light, heat, electricity, and magnetism • Properties and changes of properties in matter • Motions and forces
Core Content: Light refraction • Divergent, parallel and convergent rays • Water drop magnification • Concave and convex water lenses • Focal distance • Lens curvature and magnification • Inverse size-distance relationship • Halftones • Printed colors • Pinholes

Life Science (content standard C)

NSES Framework: Structure and function in living systems
Core Content: Explore cellulose, hair, tiny seeds, insect parts, plant cells, and other living systems with water drop microscopes. • Model the human eye • Graph visual acquity

Earth and Space Science (content standard D)

NSES Framework: Properties of earth materials
Core Content: Explore salt crystals, sugar crystals, soil and other natural products with water drop microscopes.

Science and Technology (content standard E)

NSES Framework: Abilities of technological design • Understanding about science and technology
Core Content: Make a water-drop microscope. Explore the magnification properties of lens size and curvature. What are the trade-offs?

History and Nature of Science (content standard G)

NSES Framework: Science as a human endeavor • Nature of science • History of science
Core Content: Build a powerful single-lens microscope modeled on an original design of Dutch naturalist Anton van Leeuwenhoek (1632-1723).