Abstract

A thermal activation energy of 1.5 eV for the activation of rhodopsin is needed to reduce the rate of thermal activations below the rate of optical activation at the luminance of the absolute threshold. The thermal energy of 1.5 eV is not inconsistent with the optical threshold energy of about 1.8 eV.

© 1978 Optical Society of America

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References

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  1. A. Rose, Vision: Human and Electronic (Plenum, New York, 1975), p. 50.
  2. S. I. Vavilov, Human Eye and the Sun (Pergamon, New York, 1965), p. 96.
  3. R. W. Rodieck, The Vertebrate Retina (Freeman, San Francisco, 1973), p. 62.
  4. Where ultimate limits can be defined, the evidence is that the evolutionary processes have pushed the sensitivity of the sense organs to their limits: The threshold of vision is a few photons, the threshold of hearing is thermal noise, the threshold of chemical detection is a single molecule as in the moth.
  5. D. H. Sliney and et al., J. Opt. Soc. Am. 66, 339 (1976).
    [Crossref] [PubMed]
  6. D. R. Griffin and et al., J. Opt. Soc. Am. 37, 546 (1947).
    [Crossref] [PubMed]
  7. H. de Vries, Experientia IV/9, 357 (1948).
    [Crossref]
  8. The rate of the thermally assisted optical transitions was calculated under the assumption that the lower electronic state contains a broad uniform population of vibrational states that are thermally excited. Under this assumption, the total rate of transitions in the retina illuminated by spectral flux of I(ν) W cm−2μ m−1is given by A[I(ν)/ν3] exp (hν/kT),where A is a constant that depends on the number of molecules, the mean spontaneous life time, the energy gap, and the spectral distribution of the light.
  9. S. George, J. Gen. Phys. 35, 495 (1952).
    [Crossref]
  10. P. R. Lewis, J. Physiol. 130, 45 (1953).
  11. A. Cooper and C. A. Converse, Biochemistry 15, 2978 (1976).
    [Crossref]

1976 (2)

D. H. Sliney and et al., J. Opt. Soc. Am. 66, 339 (1976).
[Crossref] [PubMed]

A. Cooper and C. A. Converse, Biochemistry 15, 2978 (1976).
[Crossref]

1953 (1)

P. R. Lewis, J. Physiol. 130, 45 (1953).

1952 (1)

S. George, J. Gen. Phys. 35, 495 (1952).
[Crossref]

1948 (1)

H. de Vries, Experientia IV/9, 357 (1948).
[Crossref]

1947 (1)

Converse, C. A.

A. Cooper and C. A. Converse, Biochemistry 15, 2978 (1976).
[Crossref]

Cooper, A.

A. Cooper and C. A. Converse, Biochemistry 15, 2978 (1976).
[Crossref]

de Vries, H.

H. de Vries, Experientia IV/9, 357 (1948).
[Crossref]

George, S.

S. George, J. Gen. Phys. 35, 495 (1952).
[Crossref]

Griffin, D. R.

Lewis, P. R.

P. R. Lewis, J. Physiol. 130, 45 (1953).

Rodieck, R. W.

R. W. Rodieck, The Vertebrate Retina (Freeman, San Francisco, 1973), p. 62.

Rose, A.

A. Rose, Vision: Human and Electronic (Plenum, New York, 1975), p. 50.

Sliney, D. H.

Vavilov, S. I.

S. I. Vavilov, Human Eye and the Sun (Pergamon, New York, 1965), p. 96.

Biochemistry (1)

A. Cooper and C. A. Converse, Biochemistry 15, 2978 (1976).
[Crossref]

Experientia (1)

H. de Vries, Experientia IV/9, 357 (1948).
[Crossref]

J. Gen. Phys. (1)

S. George, J. Gen. Phys. 35, 495 (1952).
[Crossref]

J. Opt. Soc. Am. (2)

J. Physiol. (1)

P. R. Lewis, J. Physiol. 130, 45 (1953).

Other (5)

The rate of the thermally assisted optical transitions was calculated under the assumption that the lower electronic state contains a broad uniform population of vibrational states that are thermally excited. Under this assumption, the total rate of transitions in the retina illuminated by spectral flux of I(ν) W cm−2μ m−1is given by A[I(ν)/ν3] exp (hν/kT),where A is a constant that depends on the number of molecules, the mean spontaneous life time, the energy gap, and the spectral distribution of the light.

A. Rose, Vision: Human and Electronic (Plenum, New York, 1975), p. 50.

S. I. Vavilov, Human Eye and the Sun (Pergamon, New York, 1965), p. 96.

R. W. Rodieck, The Vertebrate Retina (Freeman, San Francisco, 1973), p. 62.

Where ultimate limits can be defined, the evidence is that the evolutionary processes have pushed the sensitivity of the sense organs to their limits: The threshold of vision is a few photons, the threshold of hearing is thermal noise, the threshold of chemical detection is a single molecule as in the moth.

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Figures (4)

FIG. 1
FIG. 1

Sun’s spectral emittance at AMO (air mass zero), normalized, and (2) standard luminosity curve (photopic).

FIG. 2
FIG. 2

(1) Sun’s spectral emittance in photons cm−2 s−1 eV−1 (normalized), (2) standard luminosity curve (photopic), and (3) night sky spectral emittance (normalized) vs. photon energy.

FIG. 3
FIG. 3

The threshold power to excite a sensation of vision as measured by Sliney et al.5 and the threshold prediction based upon thermally assisted optical transitions (see Ref. 4). Sliney’s results obtained from cones agree within half an order of magnitude with Griffin’s6 results obtained from rods and cones.

FIG. 4
FIG. 4

Assumed potential curve for the rhodopsin molecule. Dissociation through either curve leads to a sensation of vision. Excitation by path 1 is thermally assisted optical transition, path 2 represents thermal activation.

Equations (3)

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( 2 π ν 3 / c 2 ) exp ( - h ν / k T ) = 10 6 photons cm - 2 s - 1
10 16 ν * exp ( - E th / k T ) = 10 4 .
A [ I ( ν ) / ν 3 ] exp ( h ν / k T ) ,