Physiological constants (Michaelmas)

Question 1

What are the focusing elements of the eyes?

Answer 1

• Cornea: Contributes 2/3 (~48D) of overall focusing power of eyes.
• Lens: Contributes 1/3 (~18-26D) of overall focusing power of eyes.

Question 2

What is the maximum focusing power of the eyes?

Answer 2

57D

Question 3

What is the absolute threshold if luminance for vision?

Answer 3

10^-6 cd/m²

Question 4

What is the width of maximum range of sensitivity for vision?

Answer 4

~10¹⁵

Question 5

What is the accommodation range for an emmetrope?

Answer 5

12D

Question 6

What is the width of a pointspread function?

Answer 6

1.5 arc minutes (~90 arc seconds)

Question 7

What is the diameters of the pupils?

Answer 7

2-8 mm

Question 8

What is the minimum photoreceptor spacing in the retina?

Answer 8

~2.3 μm (~30 arc seconds)

Question 9

What angle is subtended by the fovea?

Answer 9

~1^o

Question 10

What angle is subtended by the optic disc?

Answer 10

~5^o

Question 11

What is the peak absorption wavelength of rods?

Answer 11

~500nm

Question 12

What is the peak absorption wavelength of red cones?

Answer 12

564nm

Question 13

What is the peak absorption wavelength of green cones?

Answer 13

534nm

Question 14

What is the peak absorption wavelength of blue cones?

Answer 14

420nm

Question 15

What is the critical fusion frequency in rod-mediated scotopic vision?

Answer 15

~15Hz

Question 16

What is the critical fusion frequency in cone-mediated photopic vision?

Answer 16

~60Hz

Question 17

What is the peak absorption wavelength of red cones?

Answer 17

558nm

Question 18

What is the peak absorption wavelength of green cones?

Answer 18

531nm

Question 19

What is the peak absorption wavelength of blue cones?

Answer 19

419nm

Question 20

What is the normal hearing range for humans?

Answer 20

20Hz - 20kHz

Question 21

What is the minimum sound pressure detectable by the human ear?

Answer 21

20μPa

Question 22

What is roughly the pain threshold for hearing at all frequencies?

Answer 22

~120dB SPL

Question 23

What is the transformer ratio of the middle ear apparatus?

Answer 23

18.2

Question 24

What is the resting potential of endolymph?

Answer 24

+100 mV

Question 25

What is the number of axons in the cochlear nerve?

Answer 25

~30,000

Question 26

What is the minimum and maximum interaural time differences detectable by the ears?

Answer 26

10 - 660μs

Question 27

What is the minimum interaural intenisty difference detectable by humans?

Answer 27

1 dB