Light Flashcards
(92 cards)
Cataracts
The lens in the eye becomes opaque because of protein denaturation that inhibits some wavelengths entering. Decreases the blue spectrum
Physical nature of light
Provides energy (direct or indirect) and provides information about the world around us
How the sun works
Converting hydrogen into helium, which converts matter into energy (EMR)
EMR
Energy that travels in waves at the speed of light.
Wavelength range of EMR
10^-12-10^6 (cosmic to radio waves)
Light
The portion of EMR that humans can detect with their eyes. 400-700 nm
Physics definition of light
Also includes ultraviolet and infared
Wave particle duality
Has no mass, is a wave and a photon particle. Creating a wave of photons.
Wavelength and energy relationship
Inverse
3 options for a photon hitting something
- Reflected
- Transmitted through
- Absorbed (the only way it can be used as energy)
Absorption process
A photon is transferred to an electron in a molecule. The electron is excited out of ground state, that state can be used for energy
Absorption only happens if
The energy of the photon exactly matches the amount needed to excite the electron
Pigment
Molecules that are good at absorbing light such as chlorophyll, retinal, and indigo
Why is pigment a good absorber
Because of the conjugated system.
Conjugated system
A region where carbon atoms covalent bonds alter single and double causing a delocalization of electrons. They are not busy so they can interact with photons
Colors of pigments
Every chemical structure has a unique energy and therefore absorbs a unique wavelength. The color is the not absorbed wavelengths
Ultimate energy source
The sun
Photosynthesis
Plants use photons to make CO2 into glucose. Light enters the biosphere through this process.
Not all that use light as energy are photosynthetic
There is not always a conversion of CO2 to glucose
Halobacterium
Archaea that contain a light driven proton pump called bacteriorhodopsin. The energy is used but not to make glucose
Rhodopsin
A common photoreceptor. Made of opsin protein that is bended with retinal pigment
Opsin
Spans the membrane many times. Retinal is in its middle
Photons enters the eye then…
Retinal pigment changes shape, alters the opsin protein, eventually leading to vison by altering intracellular concentration
Scale of photoreceptiors
125 million receptors per eye, millions of rhodopsin per receptor