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Light: The EM Spectrum

Light: The EM Spectrum. http://www.antonine-education.co.uk/physics_gcse/Unit_1/Topic_5/em_spectrum.jpg. Light: Solar Radiation Spectrum. http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png. Light Perception: The Chromophore. all- trans -retinal. 11- cis -retinal.

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Light: The EM Spectrum

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  1. Light:The EM Spectrum http://www.antonine-education.co.uk/physics_gcse/Unit_1/Topic_5/em_spectrum.jpg

  2. Light:Solar Radiation Spectrum http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png

  3. Light Perception:The Chromophore all-trans-retinal 11-cis-retinal Diagram modified from Terakita(2005)

  4. Light Perception:Opsins I The Chromophore: Diagram modified from Terakita(2005)

  5. Light Perception:Opsins II Diagram modified from Terakita(2005)

  6. Light Perception: Photoreceptors I Diagram modified from Nilsson and Arendt(2008)

  7. Light Perception: Photoreceptors II Rhabdomeric Photoreceptor (depolarizing/ “on” receptor) = Dark-to-light detector Ciliary Photoreceptor (hyperpolarizing/ “off” receptor) = Light-to-dark detector Diagram modified from Nilsson and Arendt(2008)

  8. Light Perception: Signal Transduction

  9. From Marlow and Speiser et al(in prep).

  10. Tentacle retraction Oral disk flexion Tentacle flexion Response Wavelength (nm) From Clark and Kimmeldorf (1977).

  11. Building an Eye Components: Depolarizing photoreceptor ("on" receptor) Pigment layer Hyperpolarizing photoreceptor ("off" receptor) Mirror Light path Lens Diagrams by Dan Speiser

  12. Optics concept 1:Refraction Refraction is the deflection from a straight path undergone by a wave (such as light) when it passes obliquely from one medium (such as air) into another medium (such as water) in which its velocity is different.

  13. Camera Eyes: Lens optics Camera eye w/ depolarizing photoreceptors and a lens (ex. squid and octopi) Camera eye w/ hyperpolarizing photoreceptors and a lens (ex. fish) Diagrams by Dan Speiser

  14. Camera Eyes: Corneal optics Camera eye w/ depolarizing photoreceptors and corneal optics (ex. land spiders) Camera eye w/ hyperpolarizing photoreceptors and corneal optics (ex. land vertebrates) Diagrams by Dan Speiser

  15. Big Concept 2:Trade-offs (part 1) Optical resolution ≈ Inter-receptor angle (ΔΦ) = s/f Optical sensitivity (S) ∝ D2Δρ2(where Δρ= d/f) D f f s d

  16. Compound Eyes Basic compound eye w/ depolarizing photoreceptors at the base of pigment tubes (ex. many inverts) Diagrams by Dan Speiser

  17. Compound Eyes II:Trade-offs (Part II) Apposition compound eye w/ depolarizing photoreceptors and lenses (ex. diurnal insects) Diagrams by Dan Speiser

  18. Compound Eyes III Reflecting superposition eye with depolarizing photoreceptors (ex. decapod shrimp and lobsters) Diagrams by Dan Speiser

  19. Big Concept 2:Trade-offs (part 2) Ɵi f d An eye gathers light from an area with an angular size of, say, 10° A naked photoreceptor gathers light from an entire hemisphere All else being equal, a naked photoreceptor will be 130x more sensitive than an eye with an angular resolution of 10°.

  20. = 10 μm Lens Big concept 1:Convergence (part 2)

  21. Big Concept 2:Trade-offs (part 2) • Eyes allowed chitons to distinguish 10° objects from shadows. • However, eyes decreased optical sensitivity: we found that chitons without eyes responded to changes in illumination of 1%, while chitons with eyes only responded to changes in illumination of 5% or greater. • Eyeless chitons also responded to faster-moving objects.

  22. Back to eye diversity . . . “Bivalve lineages may be aptly described as evolutionary eye factories, in the sense that they have developed eyes of many different types, often at unusual positions of the body” - Dan-E. Nilsson

  23. Scallop (Aequipecten)

  24. ? File shell (Lima scabra)

  25. + Turkey wing (Arca zebra)

  26. ? Giant Clam (Tridacna)

  27. ? Lantern Shell

  28. ? Cockle (Dinocardium)

  29. DAPI Anti-tubulin Autoflourescence = 100 μm Lens Distal retina Proximal retina Mirror

  30. Table modified from Land and Nilsson (2002).

  31. DAPI Anti-tubulin Autoflourescence = 100 μm Optical resolution ≈ Inter-receptor angle (ΔΦ) = s/f Receptor spacing (s) = the distance between adjacent receptors Focal length (f) of a concave spherical mirror = 0.5 x the radius of the mirror Mirror

  32. Optics concept 2:Spherical aberration An camera eye with a lens that causes spherical aberration A camera eye with a lens that does not cause spherical aberration (due to, for instance, having a graded refractive index)

  33. Optics concept 2:Spherical aberration (in the scallop eye) A spherical mirror w/ no lens = more spherical aberration A spherical mirror w/ correcting lens = less spherical aberration

  34. Optics concept 3:Chromatic aberration (prism)

  35. Optics concept 3:Chromatic aberration Chromatic aberration in a camera eye Chromatic aberration in a scallop eye

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