Why is a shadow longer when the lamp is low?

Picture your room at bedtime, with a lamp glowing warm and yellow. Your teddy bear sits on the floor near the lamp. Look at the floor on the other side of your teddy. A dark teddy shape lies there, quiet and still.

Now a grown-up sets the lamp down low, close to the floor. Whoosh, the dark teddy shape stretches far across the rug! Why is a shadow longer when the lamp is low?

Light from the lamp cannot pass through the teddy. The teddy blocks it, so the floor on the other side of the teddy gets no light. That dark spot is the teddy's shadow.

Light from a lamp travels in beams, which means straight lines of light. A beam never bends around the teddy. It flies straight, like a ball rolling on a smooth floor.

When the lamp sits high above the teddy, its beams point down steeply, like a slide. The beam over the teddy's head lands on the floor close to the teddy. Only a little bit of floor stays dark. That makes the shadow short.

When the lamp sits low, its beams come slanting, which means leaning low across the room. They skim along near the floor, right beside the teddy. Where do you think the beam over the teddy's head will land now?

It lands far, far away! The slanting beam slips just over the teddy's ears. Then it glides a long way before it touches the floor.

All along that path, from the teddy to where the beam lands, the floor gets no light. The dark spot stretches long. That long dark spot is the teddy's long shadow.

The teddy blocks the lamp's light. A low lamp's slanting beams land far past the teddy, so its shadow stretches long.

The lamp glows low and warm beside the rug. Your teddy sits still, and its dark shape reaches all the way across the floor.