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Chapter 1

Chapter 1 Light and Life Summary notes of the entire chapter, covers important topics in detail, with definitions, and focus on important topics covered in lecture

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Diane Williams

BI110CHAPTER 1LIGHTLIFE11 The Physical Nature of LightLight sustains all life and provides organisms with information about the physical world11a What is Lightlight is energy created by the sun by converting hydrogen into helium at such an extreme rate that it converts 4 million tons of matter per secondenergy is released as electromagnetic radiation which comes in two forms electrical and magnetic traveling at 90 degree to one anotherLight can be defined as the portion of the electromagnetic spectrum that humans can detect with their eyes or as a narrow bang of the electromagnetic spectrum spanning the wave lengths in nanometres approx 380nm750nmLight also behaves as a stream of photons Photons have no mass but contain a precise amount of energy which is inversely related to its wavelengthSHORT WAVELENGTHHIGH ENERGY blue lightLONG WAVELENGTHLOW ENERGY red light11b Light Interacts With MatterAlthough light has no mass it is able to interact with and change matter allowing it to be used by living thingsLight can do one of three things when it comes in contact with an object1 Reflect off the object2 Transmit through the object3 By absorbed by the objectPigment a molecule that can absorb photons of light Individual pigments differ in the wavelengths of light they can absorbPigments share a common feature critical to light absorption called a conjugated systemConjugated System a region where carbon atoms are covalently bonded with alternating single and double bonds Results in the delocalization of electrons thus they more readily interact with the photons11c Why is Chlorophyll GreenAbsorption of light occurs when the energy of a photon is transferred to an electron of the pigment molecule1A single photon results in the excitation of ONE electron in a pigment molecule2The energy of the photon must match the energy difference between the ground state and one of the excited states in order for the photon to be absorbedrecall that each photon has a precise amount of energy
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