Paper 1 - Eye Problems / The Eye

Question 1

What is long sightedness ?

Answer 1

Long sighted people can focus on distant objects but not short ones. Rays of light focus ‘AFTER’ the retina. May have eyeballs that are too short or eye lenses that are not powerful enough, or cornea not curved enough - happens with age, lens does not bend enough. This can be corrected using spectacles with CONVERGING lenses. A converging lens brings the rays together so light is focused on the retina

Question 2

What is short sightedness ?

Answer 2

Short-sighted people can focus on close objects but not distant ones. Rays of light focus in FRONT of the retina. May have eyeballs that are too long or eye lenses that are too powerful even when relaxed, or cornea is too curved. This can be corrected using spectacles with DIVERGING lenses. A diverging lens makes the rays come together further away so light is focused on the retina

Question 3

Other solutions to Long and short sightedness

Answer 3

Long and short sightedness can also be corrected with laser surgery and with contact lenses - work with ghe eye’s lens to adjust the pathway of light through the eye.

Question 4

How do cataracts form and how are they treated ?

Answer 4

Cataracts occur when the lens becomes cloudy, so light cannot pass through it properly. The persons retina receives a blurred image. Cataracts can be treated by replacing the cloudy lens with an artificial lens.

Question 5

What is colour blindness / how does the eye retain colour?

Answer 5

Normally a retina contains three type of cones that detect red, green and blue light. The colour of an image is detected by how much each type of cone is stimulated. Colour blindness occurs when at least one type of cone is missing or does not work properly - inherited disorder mostly in males

Question 6

What are cones in the eye ?

Answer 6

Cones are Receptor cells that are sensitive to the color of light (in the retina) cones generate impulses in sensory neurones which lead into the brain through the optic nerve - passed into full colour vision at the back of the cerebral hemispheres.

Question 7

What are rods in the eye ?

Answer 7

Receptor cells (retina) that detect differences in light intensity. Rods work well in dim light, cones only in bright light which is why colour vision is poor in dim light. Processed as shades of dark and light

Question 8

How does light pass through the eye ?

Answer 8

Enters the eye through the pupil. Cornea and lens focus the light to form a sharp image on the retina - contains receptor cells that detect the light to form an image. Nerves in the retina convert the image into electrical signals that are sent to the brain along the optic nerve.

Question 9

What is the pupil and how is it controlled ?

Answer 9

The dark area in the middle of the eye where light enters. Amount of light controlled by ciliary muscles in the iris which can either :
-constrict the pupil (decrease diameter)
-dilate it (increase diameter)
To control the amount of light entering the eye depending on conditions - bright/dim

Question 10

(WORKED EXAMPLE) explain the role if the two different kinds of receptor cells in the retina (2 marks)

Answer 10

Cone cells are sensitive to bright light and respond to different colours. Rod cells are sensitive at low light intensity and respond only to how light or dark something is.

Question 11

What is the sclera ?

Answer 11

Sclera

The white of the eye; the opaque protective outer layer.

Question 12

What is the function of the cornea

Answer 12

The transparent frontal portion of the eye, responsible for refracting light.

Question 13

What are suspensory ligaments?

Answer 13

A ring of fibres that connect ciliary muscles to the lens

Question 14

Components of the eye .

Answer 14

Retina
Iris
Lens
Cornea
Optic nerve
Ciliary muscle
Sclera
Rod cell
Cone cell

Question 15

What Is accommodation of the lens ?

Answer 15

Process of lens changing shape to focus on objects of varying distances. By Ciliary muscles and suspensory ligaments

Question 16

Accommodation of eye due to a distant object

Answer 16

Relaxation of Ciliary muscles and tightening of suspensory ligaments. Lens flatter and thinner resulting in a minor refraction of light rays.

Question 17

Accommodation of lens due to focus on a close object

Answer 17

Contraction of Ciliary muscles and loosening of suspensory ligaments - lens become thicker and rounder resulting in significant refraction of light rays

Question 18

Example of reflex in the eye.

Answer 18

The control ofpupilsize by theirisin response to light changes is an example of areflexaction.

Question 19

Ways of treating eye defects aside from glasses.

Answer 19

Contact lenses and laser eye surgery can also correct these issues. Synthetic lenses can replace faulty lenses with cataracts.

Question 20

How do cataracts resultingly form ?

Answer 20

Cataracts are caused by a build-up of protein on the lens, that make the pupil cloudy.

Question 21

What is colour blindness affected by - inherited.

Answer 21

It is caused by defects in the cone cells. Cone cells (detect light colour) and rod cells (detect light intensity) are photoreceptors (light-sensitive cells in the retina).