When driving you need to be able to clearly see road signs and traffic some dist

Question

When driving you need to be able to clearly see road signs and traffic some distance ahead of you as well as the dashboard in your car. Assume that you have a normal lens-to-retina distance (2 cm).

a) what minimum optical power of the eye is needed to clearly see a road sign 200 m ahead?

b) what maximum optical power is needed to clearly see the dashboard 40 cm away?

c) what range of accomadation is needed?

d) if you can accomodate at a maximum rate of 1.1 dioptres per second, how long does it take your eyes to adjust when looking up at the road from the dashboard?

e) If you are traveling on the open road at 100 km/h, how far do you travel in the time it takes your eyes to accommodate between the dashboard and the road?

Explanation / Answer

a)
s = 200 m
s' = 2 cm = 0.02 m
1/f = 1/s' + 1/s
p = 1/0.02 + 1/200
    =50.005 D

b)
s = 40 m
s' = 2 cm = 0.02 m
1/f = 1/s' + 1/s
p = 1/0.02 + 1/40
    =50.025 D

c)
range of accomodation = 50.025 - 50.005 = 0.02 D

d)
t = range / speed
   = 0.02 D / (1.1 D/s)
   =0.018 s
   = 18 ms
Answer: 18 ms

I am allowed to answer only 4 parts at a time

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