Which part of the eye contains the light receptor cells?

retina. Rods and cones are in the retina.

What does the iris do?

controls how much light enters the eye. It changes the size of the pupil.

What happens to the pupil in dim light?

It gets larger. More light is let in.

What carries impulses from the eye to the brain?

the optic nerve. The impulses come from the receptors in the retina.

What shape is the lens when looking at a near object?

fat. A more curved lens bends light more.

The eye · Cambridge IGCSE Biology (9

In plain words

Your eye works like a camera. Light comes in through a clear window at the front, is focused by a lens, and lands on a screen of light-sensitive cells at the back. In bright light the opening shrinks to protect that screen.

Three things to know

Cornea: the clear front, which bends (refracts) light. Iris: the coloured ring that controls how much light gets in through the pupil. Lens: focuses light on the retina. Retina: contains the light receptor cells. Optic nerve: carries impulses to the brain.
The pupil reflex: in bright light the pupil gets smaller, protecting the retina; in dim light it gets bigger, to let more light in.
Focusing: to see a near object the ciliary muscles contract, the suspensory ligaments slacken, and the lens becomes fatter. For a distant object it is the reverse and the lens is thin.

Tips and tricks

Near object: fat lens. Distant object: thin lens. Fat lenses bend light more.
In the pupil reflex it is the iris that does the work; the pupil is just the hole.

5 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

The eye: 5 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

Which part of the eye contains the light receptor cells?
- cornea
- lens
- retina (the answer)
- iris
Rods and cones are in the retina.
What does the iris do?
- focuses light
- controls how much light enters the eye (the answer)
- carries impulses to the brain
- refracts light
It changes the size of the pupil.
What happens to the pupil in dim light?
- It gets larger. (the answer)
- It gets smaller.
- It closes.
- It changes colour.
More light is let in.
What carries impulses from the eye to the brain?
- the cornea
- the lens
- the optic nerve (the answer)
- the iris
The impulses come from the receptors in the retina.
What shape is the lens when looking at a near object?
- thin
- fat (the answer)
- flat
- hollow
A more curved lens bends light more.

5 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 8 marks. Write your answers on paper, then check them.

The eye

Cambridge IGCSE Biology (9–1) 0970 · 8 marks · papermunch.org

Name ______________________________ Date ______________

State the function of the cornea, the iris and the retina.[3]
Show answerHide answer
Cornea: refracts light. Iris: controls the amount of light entering the eye. Retina: contains the light-sensitive receptor cells.
I got this one
Describe and explain what happens to the pupil in bright light.[2]
Show answerHide answer
It gets smaller, so less light enters the eye. This protects the retina from damage.
I got this one
Describe how the eye focuses on a nearby object.[3]
Show answerHide answer
The ciliary muscles contract, the suspensory ligaments slacken, and the lens becomes fatter (more curved), so it refracts the light more.
I got this one

Answers: The eye

1. Cornea: refracts light. Iris: controls the amount of light entering the eye. Retina: contains the light-sensitive receptor cells.
2. It gets smaller, so less light enters the eye. This protects the retina from damage.
3. The ciliary muscles contract, the suspensory ligaments slacken, and the lens becomes fatter (more curved), so it refracts the light more.