Light & Seeing in the Dark

Activities to try

1. 1

   Dark den: does the light leave, or the dark arrive?

   Why it works: We can only see objects when light reaches them and our eyes; in genuine darkness there is nothing to see no matter how long we wait. The teddy did not leave — the light did. Dark is light that is absent, not a thing that arrived.

   1. Before the light goes out, predict aloud what you will see: will the objects slowly appear if you wait, or vanish? Say why first.
   2. Sit in a carefully planned, as-dark-as-possible den/blackout tent with everyday objects — a teddy, a book, a cup — and a small torch or lamp nearby, under adult supervision.
   3. With the light off, notice whether you can see the objects. If the den is truly dark you cannot see them at all; if you can see them faintly, hunt for where a little light is getting in. Name what else you can tell using touch and hearing.
   4. Turn on a small light and watch the objects reappear; describe what actually happened versus your prediction.
   5. Sweep a torch beam around and report which objects become visible — mainly the ones the beam reaches (light bouncing off nearby walls may light others faintly).
2. 2

   Dimmable scene: run the disappearance yourself

   Why it works: Lowering the light makes non-luminous objects disappear even though they are still there, while a light source stays visible in the dark. Light must reach an object for it to be seen.

   1. Look at a cosy bedroom scene with a brightness control (a slider or a light-switch, optionally with a torch).
   2. Predict what will happen to each object as you lower the light, then slowly drag the brightness down to zero.
   3. Notice which things fade and vanish (the teddy, book, cup) and which one still glows in the dark (a switched-on screen or night-light that stays on) because it makes its own light.
   4. Flick on the torch and sweep its cone around; report that only objects the beam reaches pop back into view while everything outside the cone stays invisible.
   5. Run the dimming several times to confirm the same thing happens each time.
3. 3

   Sort: makes its own light vs needs light to be seen

   Why it works: Some objects give off their own light (sources); most objects we see only reflect light that reaches them. Being bright or shiny does not make something a light source.

   1. Take a mixed set of objects — lamp, screen, glow-stick, torch (sources); teddy, book, spoon, a mirror, the Moon (non-sources/reflectors).
   2. Sort each into 'makes its own light' or 'only seen when light reaches it'.
   3. Use a lights-off test: in a dark space, which objects still show (switched-on or glowing sources) and which disappear? Remember a lamp, torch or screen makes light only while it is switched on.
   4. Decide where the Moon goes and explain: it is visible because it bounces light from the Sun, so it does not make its own light.
   5. Say in your own words what you need in order to see any of the objects that do not make their own light.