The Human Eye and the Colourful World: common misconceptions

If your child says… “The picture forms on my pupil.”

Ask together

Do the rays meet at the pupil or on the retina?

What’s true

The pupil admits light, and the iris adjusts its size.

If your child says… “My retina moves backwards to focus.”

Ask together

If the lens changes its focus, does the retina need to move?

What’s true

The distance between lens and retina stays unchanged during focusing.

If your child says… “Myopia needs a convex lens.”

Ask together

If light already gathers too soon, would gathering it more help?

What’s true

A concave lens spreads light so the myopic eye focuses it farther back.

If your child says… “Bifocals have the same power everywhere.”

Ask together

Why divide the lens if both regions do the same job?

What’s true

The two regions provide different focusing powers.

If your child says… “The prism makes new colours.”

Ask together

What would bringing all those separated colours together produce?

What’s true

White light already contains these colours; this glass prism bends violet most and red least.

If your child says… “The star itself keeps flickering.”

Ask together

Why might a low star flicker more through a longer path in air?

What’s true

Changing air alters how much starlight reaches our eyes.

If your child says… “The rising Sun is exactly where it appears.”

Ask together

Does the arriving ray point back towards the actual Sun or the apparent Sun?

What’s true

The Sun can appear above the horizon while its actual position is below it.

If your child says… “The sky reflects the blue ocean.”

Ask together

What can send blue light towards us even without an ocean underneath?

What’s true

Air molecules send scattered blue sunlight towards our eyes.