Question

Hearing level in dB (ANSI, 1996) -10 0 10 20 30 40 50 60 70 80 90 100 110 Frequency in Hertz (Hz) 125 250 500 1000 2000 4000 8000 Hz Question 4a. You see a person in the distance. From Figure 1 assume the person of height 'AB' is reflected onto the retina through the nodal point 'n' as 'ab'. If AB is 2 m in height and 10 m from the nodal point n, what will be the size of the person ('ab') on the retina in mm? Show your calculations. (Hint use basic trigonometry). (5 Marks) 17mm 100 m A 2 m B Figure .1 Question 4b. Your visual acuity can be tested using a Snellen Chart (see Figure 2 below). The smallest row that can be read can indicate your visual acuity in that specific eye. Assume you can read letters at 8 mm heigh (row 8) at a distance of 20 feet (6 m). What height are these letters on the surface of your retina (fovea)? Again, show your calculations. What is the significance of this value? (5 Marks)

          Hearing level in dB (ANSI, 1996)
-10
0
10
20
30
40
50
60
70
80
90
100
110
Frequency in Hertz (Hz)
125 250 500 1000 2000 4000 8000 Hz
Question 4a.
You see a person in the distance. From Figure 1 assume the person of height 'AB' is
reflected onto the retina through the nodal point 'n' as 'ab'. If AB is 2 m in height and 10
m from the nodal point n, what will be the size of the person ('ab') on the retina in mm?
Show your calculations. (Hint use basic trigonometry). (5 Marks)
17mm
100 m
A
2 m
B
Figure .1
Question 4b.
Your visual acuity can be tested using a Snellen Chart (see Figure 2 below). The smallest
row that can be read can indicate your visual acuity in that specific eye. Assume you can
read letters at 8 mm heigh (row 8) at a distance of 20 feet (6 m). What height are these
letters on the surface of your retina (fovea)? Again, show your calculations. What is the
significance of this value? (5 Marks)

Hearing level in dB (ANSI, 1996)
-10
0
10
20
30
40
50
60
70
80
90
100
110
Frequency in Hertz (Hz)
125 250 500 1000 2000 4000 8000 Hz
Question 4a.
You see a person in the distance. From Figure 1 assume the person of height 'AB' is
reflected onto the retina through the nodal point 'n' as 'ab'. If AB is 2 m in height and 10
m from the nodal point n, what will be the size of the person ('ab') on the retina in mm?
Show your calculations. (Hint use basic trigonometry). (5 Marks)
17mm
100 m
A
2 m
B
Figure .1
Question 4b.
Your visual acuity can be tested using a Snellen Chart (see Figure 2 below). The smallest
row that can be read can indicate your visual acuity in that specific eye. Assume you can
read letters at 8 mm heigh (row 8) at a distance of 20 feet (6 m). What height are these
letters on the surface of your retina (fovea)? Again, show your calculations. What is the
significance of this value? (5 Marks)

Added by Amy C.

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