What does the iris do?

It controls the size of the pupil, and so how much light enters the eye.

What do the receptors in the retina do?

They detect light and turn it into electrical impulses.

What is the job of the optic nerve?

To carry impulses from the retina to the brain.

What happens to the pupil in bright light, and why?

It gets smaller, so less light enters and the retina is protected.

What happens to the pupil in dim light?

It gets larger so that more light enters the eye.

Why is the pupil reflex a reflex?

It is automatic and fast, and does not involve conscious thought.

Define accommodation.

The change in shape of the lens to focus on objects at different distances.

How does the eye focus on a near object?

Ciliary muscles contract, suspensory ligaments slacken and the lens becomes thicker.

How does the eye focus on a distant object?

Ciliary muscles relax, suspensory ligaments are pulled tight and the lens becomes thinner.

What causes short sight?

An eyeball that is too long or a lens that is too strong, so light focuses in front of the retina.

What causes long sight?

An eyeball that is too short or a lens that is too weak, so light focuses behind the retina.

The eyeIB MYP Biology: Flashcards

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Question

Which part of the eye does most of the refraction of light?

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Which part of the eye does most of the refraction of light?: The cornea.
What does the iris do?: It controls the size of the pupil, and so how much light enters the eye.
What do the receptors in the retina do?: They detect light and turn it into electrical impulses.
What is the job of the optic nerve?: To carry impulses from the retina to the brain.
What happens to the pupil in bright light, and why?: It gets smaller, so less light enters and the retina is protected.
What happens to the pupil in dim light?: It gets larger so that more light enters the eye.
Why is the pupil reflex a reflex?: It is automatic and fast, and does not involve conscious thought.
Define accommodation.: The change in shape of the lens to focus on objects at different distances.
How does the eye focus on a near object?: Ciliary muscles contract, suspensory ligaments slacken and the lens becomes thicker.
How does the eye focus on a distant object?: Ciliary muscles relax, suspensory ligaments are pulled tight and the lens becomes thinner.
What causes short sight?: An eyeball that is too long or a lens that is too strong, so light focuses in front of the retina.
Which lens corrects short sight?: A concave (diverging) lens.
What causes long sight?: An eyeball that is too short or a lens that is too weak, so light focuses behind the retina.
Which lens corrects long sight?: A convex (converging) lens.

Exam questions on The eye

Amara walks from a bright street in Lagos into a dimly lit cinema. For a few moments she can see very little, then her vision gradually improves. When she leaves after the film, the bright sunlight is uncomfortable at first.
Explain how Amara's pupils respond when she leaves the cinema, and why this response is useful.2 marks
Kenji is reading a message on his phone, held close to his face. He then looks up to read a road sign on the other side of the street.
Explain how the eye changes so that Kenji can focus on his phone.2 marks
A class investigates the pupil reflex. One student sits in a room where the light intensity can be changed. After one minute of adjusting to each light level, a partner holds a ruler beside the student's eye and estimates the pupil diameter. The results were: 7.5 mm at 10 lux, 5.0 mm at 100 lux, 3.0 mm at 1000 lux and 2.0 mm at 10 000 lux.
Describe the trend in the results and use the data to support your answer.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).