26. f = focal length power of a lens = 1 ---------- f (m) f = 1 m: power = 1 D f = 2 m: power = 0.5 D f = 0.5 m: power = 2 D + 1 D: converging lens - 1 D: diverging lens
27.
28.
29.
30.
31.
32.
33.
34.
35. emmetropia: unaccommodated eye emmetropia: accommodated eye myopia: distant objects, forms in front of retina correction: - lens, decreases power MYOPIA
36.
37. emmetropia: unaccommodated eye emmetropia: accommodated eye hypermetropia: image forms behind the retina correction: + lens, increases power HYPERMETROPIA
49. a rod outer segment inner segment in light when light strikes the outer segment, Na+ channels close Na+ influx ceases inner segment pumps Na+ out leads to hyperpolarised membrane Na + Na + Na + - 80 mV Na + in dark Na + Na + Na + membrane potential - 40 mV
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51.
52. wavelength 400 700 500 600 light absorption spectrum Ultra violet violet indigo blue green yellow orange red Infra red visible spectrum rods
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55.
56. 0 10 20 30 40 50 1 10 100 1000 10000 100000 cone adaptation rod adaptation minutes in dark retinal sensitivity
57. 0 10 20 30 40 50 minutes in dark retinal threshold