The eye's response to light

Question 1

Cornea

Answer 1

a transparent, convex membrane that protects the front part of the eye and bends light rays inwards to help focus light inside the eye

Question 2

Pupil

Answer 2

adjustable opening in the centre of the iris which allows light into the inner part of the eye

Question 3

Iris

Answer 3

– the muscle that surrounds the pupil and expands and contracts to allow more or less light into the pupil

Question 4

Lens

Answer 4

– a transparent, convex structure behind the iris that changes shape to focus light into the image on the retina. Convex shape inverts the image, lens bulges to see close objects and flattens to see distant ones

Question 5

Ciliary muscles

Answer 5

are attached to each end of the lens and change its shape, contracting to bulge the lens out and relaxing to flatten the lens

Question 6

Retina

Answer 6

a light sensitive membrane composed of a number of layers of specialised neurons at the back of the eye, the receiving area for light images. Very back layer consists of photoreceptors, cells specialised to detect and respond to light, which convert light waves into electrochemical energy to be sent to the receptors that form the front layers of the retina

Question 7

Optic nerve

Answer 7

a bundle of the front layer receptors’ axons (fibres that carry information away from the neuron’s cell body), which is the neural pathway for visual stimuli to travel from the eye to the brain, and exits the brain through an opening in the retina (blind spot) and ends in the brain’s occipital lobe

Question 8

What is the blind spot?

Answer 8

• opening in the retina where the optic nerve exits the eye.
• no photoreceptors there to detect and respond to the part of the light image that strikes it, and
• gap in the visual information sent to your brain by photoreceptors
• brain fills in gap using psychological processes
• visual cortex of the brain actively extends patterns from surrounding areas so that they fill the gap made by the blind spot

Question 9

Nanometres

Answer 9

a billionth of a metre; the measurement for light

Question 10

Visible light spectrum

Answer 10

range of wavelengths to which the human eye is sensitive