Page 96 - Science Course 3 (Book 2)

Mo10-L6c: How Does the Human Eye Work?

When the iris changes size, the amount of light that The retina is a layer of special light-sensitive cells in
enters the eye changes. the back of the eye.

The iris relaxes in bright light

In the retina, chemical reactions produce nerve
signals that the optic nerve sends to your brain.

Rod cells and cone cells are two types of light-
sensitive cells in your retina.
The iris contracts in dim light

Rod Cells
Cone Cells
The lens enables the eye to form a sharp image of
nearby and distant objects. The muscles surrounding Rod cells enable people to see objects in dim light.
the lens change the lens’s shape. Cone cells enable people to see colors.

The retina has three types of cone cells, which
respond to a different range of wavelengths.

Key Concept

How Does the Human Eye Work?
Lens becomes rounder
and a sharp image form Identify the parts of the eye that form a sharp
of a nearby object. image of an object and the parts that convert an
image into electrical signals.
Lens is rounder

Lens becomes f atter
and a sharp image forms
of a distant object.
Lens is f atter

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