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Topic ladders · Physics

Light

One topic, four rungs: from Classes 1–3 to Classes 11–12. Start at your own stage, or climb from the bottom. Every rung follows the same six steps: Notice, Guess, Try, Observe, Explain, Ask another question.

Print the family table: all four rungs side by side on one sheet, so everyone at home can find their own rung.

Choose your class stage

Rung 1 · Classes 1–3

Light and Shadows

Before you start: safety and help

For the grown-up who helps.

  • Safety: Do not shine bright light into anyone's eyes.
  • Good questions: "Is the object blocking the light?"
  • Answer to step 6: when the light moves closer to the object, the shadow gets bigger.

What you need

  • Torch or phone light
  • Different objects (toy, hand, book, clear plastic bottle, butter paper, opaque box)
  • Wall or white paper screen

Child steps

  1. Notice. When is a shadow formed? Look at your own shadow.
  2. Guess. What kind of objects will make a dark shadow? Which will make a faint one or almost none?
  3. Try. Shine the light on different objects and look at the shadows.
  4. Observe. Which objects make clear dark shadows? Which let some light pass through? Which let almost all the light through?
  5. Explain. Tell someone why some objects make shadows and others do not.
  6. Ask another question. What happens to the shadow when you move the light closer or farther?
For teachers
  • Learning aims: Understand that light travels in straight lines and that opaque objects block it and form shadows.
  • Key vocabulary: light, shadow, opaque, translucent, transparent, block.
  • Review: Children sort objects into three groups: dark shadow (opaque), faint shadow (translucent), almost no shadow (transparent).

Rung 2 · Classes 4–7

Reflection of Light

Before you start: safety and help

For the grown-up or teacher who helps. Students: read it too, so you know the rules.

  • Safety: Do not use a laser pointer, even a toy one. Tape the mirror edges. Work in a dim room so the beam shows clearly.

What you need

  • Small plane mirror (with taped edges) and a lump of clay or a book to stand it up
  • Torch, a comb or a card with a thin slit (to make a thin beam)
  • White paper, pencil, ruler, protractor

Student steps

  1. Notice. Look at yourself in a mirror. Where does the light come from and where does it go?
  2. Guess. If light hits a mirror at an angle, at what angle will it bounce off?
  3. Try. Stand the mirror on the paper and draw a line along its front. Draw a line at right angles to the mirror (the normal). Shine a thin beam at the mirror where the normal meets it, and mark the path of the incoming and reflected beams with dots.
  4. Observe. Measure the angle between the incoming beam and the normal, and between the reflected beam and the normal.
  5. Explain. What rule can you state about how light reflects from a plane mirror?
  6. Ask another question. What happens if you use two mirrors? Can you make light turn a corner, like a periscope?
For teachers
  • Learning aims: Observe and state the law of reflection (angle of incidence = angle of reflection, both measured from the normal); understand that smooth surfaces reflect light regularly.
  • Key vocabulary: reflection, incident ray, reflected ray, normal, angle, plane mirror.
  • Common error: measuring from the mirror surface. The rule still works that way, but the standard angles are from the normal, and students must use one method consistently.
  • Review: Students demonstrate and explain the equal-angle rule.

Rung 3 · Classes 8–10

Refraction and Lenses

Before you start: safety and help

For the grown-up or teacher who helps. Students: read it too, so you know the rules.

  • Safety: Never point the lens at the Sun, never look at the Sun through it, and never leave it in sunlight: it can burn skin, start a fire and damage eyes.
  • Help with focusing the image clearly.

What you need

  • Glass of water, pencil or straw
  • Convex lens (magnifying glass)
  • White paper or card, a room with a bright window (or a lamp)

Student steps

  1. Notice. A pencil looks bent when placed in a glass of water. Why?
  2. Guess. What happens to light when it passes from air into water or through a lens?
  3. Try. Observe the bending of a pencil in water from the side. Then, on the side of the room away from a bright window, hold the lens between the window and a white card, and move the card until a sharp image of the window appears on it.
  4. Observe. Record where the image is formed (how far from the lens) and whether it is upside down, larger or smaller. Then look through the lens at small print held close: what is different?
  5. Explain. Link your observations to the idea that light changes speed when it enters a different material, and changes direction if it enters at an angle.
  6. Ask another question. How are lenses used in cameras, eyes, and spectacles?
For teachers
  • Learning aims: Observe refraction; understand that lenses bend light and can form images.
  • Key vocabulary: refraction, lens, convex, image, focus, focal length.
  • Expected results: the image of a distant window on the card is real, upside down and smaller. Close up, the lens gives an upright, enlarged image you see through the lens (this one cannot be caught on a card). The distance from lens to card for a distant window is roughly the focal length.
  • Review: Students explain why the pencil appears bent and how a lens forms an image.

Rung 4 · Classes 11–12

Investigating Optical Phenomena

Before you start: safety and help

For the grown-up or teacher who helps. Students: read it too, so you know the rules.

  • Safety: School laboratory with a teacher. Use only the school's low-power laser, never point it at anyone, keep the beam below eye level, and remove shiny watches and jewellery. Never view the Sun through any optical instrument.

What you need

  • School-laboratory kit for the chosen investigation (mirrors, lenses, glass block, prism, diffraction grating, spectrometer if available, low-power laboratory laser, screen)

Student steps

  1. Notice. Light shows reflection, refraction, dispersion, interference and diffraction under different conditions.
  2. Guess / Hypothesise. Choose one optical phenomenon and predict quantitative or qualitative behaviour.
  3. Try. Design and carry out a controlled investigation (e.g., focal length of a lens using 1/f = 1/v − 1/u with the sign convention your textbook uses, refractive index of a glass block, angle of minimum deviation with a prism).
  4. Observe. Collect data carefully, with repeats, and present it in tables and graphs.
  5. Explain. Analyse results using relevant formulae and discuss sources of error.
  6. Ask another question. How is this phenomenon applied in real optical instruments or natural effects (rainbows, fibre optics, etc.)?
For teachers
  • Learning aims: Plan and analyse quantitative optics experiments; apply theoretical models to data.
  • Review: Students present method, data, calculations and real-world links.

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