BTEC APPLIED SCIENCE: UNIT 11 - Learning Aim D

1. How many electrons can an s subshell hold? 2 2. How many electrons can a p subshell hold? 6 3. How many electrons can a d subshell hold? 10 4. Which subshells are available in the first energy level? 5. Which subshells are available in the second en- ergy level? 6. Which subshells are available in the third energy level? s s and p s, p and d 7. What is Hund's rule? (Think bus seats!) Every orbital in a sub- shell must be singly filled with an electron before any one orbital can be doubly occu- pied, and all electrons in singly occupied orbitals have the same spin. 8. Which elements do not fill the 4s subshell before the 3d subshell? Copper and chromium 9. Define the term ionic bond The electrostatic attrac- tion between oppositely charged ions 10. What is the charge of an ion from group 1? +1 11. What is the charge of an ion from group 2? +2 12. What is the charge of an ion from group 6? -2 13. What is the charge of an ion from group 7? -1 14. Explain how atoms of sodium react with atoms of chlorine 15. Why do ionic bonds have such high melting points? 16. State two factors that affect the strength of an ionic bond Na loses its 2s1 elec- tron gaining a +ve charge. Cl gains an electron in the 3p subshell gaining a -ve charge. The opposite charges attract to form NaCl Each +ve ion is sur- rounded by 6 -ve ions and vice versa. Strong electrostatic at- traction in every direc- tion. Requires a large amount of energy to break Size of ion and charge on ion 17. When can ionic substances conduct electricity? When molten or in aqueous solution 18. Describe the properties of ionic compounds Conduct electricity when molten or aque- ous solution High melting/boiling points Usually soluble in water 19. Define the term covalent bond A shared pair of elec- trons 20. Which metals lose electrons from the 4s sub- shell before the 3d subshell? Transition metals 21. Why do metals have such high melting points? Strong force of attrac- tion between positive 22. State the two factors that affect the strength of metallic bonding 23. Explain how the charge on metal ions affects the strength of the metallic bond 24. Explain how the size of the metal ions affects the strength of the metallic bond ions and delocalised electrons. This requires a large amount of ener- gy to overcome. Size of ion Charge on ion The larger the +ve charge the greater the attraction between the nucleus and the delo- calised electrons The smaller the +ve ion the closer the nucleus is to the delocalised elec- trons creating a greater attraction 25. Explain why metals conduct electricity The delocalised elec- trons 'carry' charge. Current flows because of this. 26. Explain why metals conduct heat Particles are packed tightly so kinetic ener- gy is passed from ion to ion. The delocalised electrons also enable heat to be passed. 27. Explain why metals are ductile and malleable The lattice structure al- lows layers of metal ions to slide over each other without disrupting bond- ing 28. Name the 3 forces between molecules Van der Waals Permanent dipole-di- 29. Order the 3 forces between molecules in order of strongest to weakest pole Hydrogen bonds Hydrogen bonds Permanent dipole-di- pole Van der Waals 30. How are Van der Waal's forces formed? Electrons move to one side, causing a tem- porary dipole. This in- duces a temporary di- pole in neighbouring molecules. Attraction occurs between oppo- sitely charged dipoles 31. In what molecules do Van der Waal's forces ex- ist? 32. How are permanent dipole-dipole forces formed? 33. In which molecules do permanent dipole-dipole forces exist? 34. Which elements must be present for hydrogen bonds to exist? Non-polar molecules Permanent dipole in one molecule attracts oppositely charged per- manent dipole in neigh- bouring molecule Polar molecules Hydrogen and either ni- trogen, oxygen or fluo- rine 35. What is meant by the term displacement? When a more reactive element takes the place of a less reactive ele- ment in a compound 36. State the equation for determining moles Moles = mass ÷ rela- tive atomic mass (molar mass) 37. Define the term Avogadro's Constant The number of atoms in a mole of a given substance. Quoted as 6.02x10^23 38. Define the term relative atomic mass The average mass of an atom of an element rel- ative to 1/12th the rela- tive atomic mass of Car- bon12 39. Define the term relative molecular mass The average mass of a molecule relative to 1/12th the relative atom- ic mass of Carbon12 40. What does this number represent? 6.02x10^23 The number of particles in a mole. Commonly called Avogadro's Con- stant 41. What is the equation for calculating % yield? % yield = (actual yield ÷ theoretical yield) x 100 42. What groups are included in the 's' block of the periodic table? 43. What part of the periodic table is known as the 'd' block? 44. Which groups are in the 'p' block of the periodic table? Groups 1 and 2 Transition metals 3, 4, 5, 6 and 7 45. What is a group on the periodic table? A vertical column 46. What is a period on the periodic table? A horizontal row 47. Define the term first ionisation energy The energy required to remove the outermost electron from one mole of gaseous atoms to produce one mole of gaseous +1 ions 48. Define the term atomic radius The distance between the nucleus of an atom and the outermost elec- tron 49. Define the term electronegativity A measure of how well an atom attracts a bond- ing pair of electrons in a covalent bond 50. Define the term malleability How easily a material can be hammered into shape 51. Define the term ductility How easily a material can be drawn into wires 52. Describe the trend in atomic radius down any group 53. Explain the trend in atomic radius down any group 54. Describe the trend in first ionisation energy down groups 1 and 2 55. Explain the trend in first ionisation energy down groups 1 and 2 Atomic radius increases Higher energy levels are filled. The orbitals in higher energy levels are further from the nucleus First ionisation energy decreases Increased electron shielding Greater atomic radius Smaller attraction to +ve nucleus 56. Describe the trend in melting points down groups 1 and 2 57. Explain the trend in melting points down groups 1 and 2 58. Describe the change in state as you go down group 7 59. Describe the change in colour as you go down group 7 60. Describe the trend in electronegativity down group 7 61. Explain the trend in electronegativity down group 7 62. Describe the trend in melting point down group 7 63. Explain the trend in melting point down group 7 SO electron is easier to remove requiring less energy Melting point decreases Strength of metallic bond is weaker due to greater atomic ra- dius decreasing attrac- tion between +ve nucle- us and delocalised elec- trons The trend is they be- come more solid (i.e. fluorine is a gas, bromine is a liquid and iodine is a solid) They become darker as you go down the group Electronegativity de- creases down the group Greater distance be- tween nucleus and bonding electrons Greater electron shield- ing Decreases attraction between nucleus and electron Melting point increases down the group 64. Describe the trend in atomic radius across a period 65. Explain the trend in atomic radius across a peri- od 66. Describe the trend in electronegativity across a period 67. Explain the trend in electronegativity across a period 68. Describe the trend in melting point across a pe- riod 69. Explain the trend in melting point across a peri- od Atomic radius increases Stronger Van der Waal's forces More energy needed to overcome the intermol- ecular forces Atomic radius decreas- es Greater nuclear charge (more protons) Same number of elec- tron shells Same amount of elec- tron shielding Electronegativity in- creases across a period Same amount of elec- tron shielding Greater number of pro- tons More attraction be- tween nucleus and bonding pair of elec- trons Melting point increas- es across the met- als and then de- creases throughout the non-metals Metallic bonding gets stronger across the pe- riod. All other intermole- cular forces are weaker 70. Why does the group 3 element have a lower first ionisation energy than the group 2 element 71. Why does the group 6 element have a lower first ionisation energy than the group 5 element than this and therefore easier to break Electron taken from p subshell rather than s subshell so is further from the nucleus. Less energy is needed to re- move the electron. Electron is taken from a paired orbital rather than a singly occu- pied orbital. Electron repulsion between the pair reduces the energy needed. 72. Define the term displacement When a more reactive element takes the place of a less reactive ele- ment in a molecule 73. Describe the trend in reactivity down group 1 They become more re- active down the group 74. Define the term reduction Reduction is gain of electrons 75. Define the term oxidation Oxidation is loss of elec- trons 76. Define the term reducing agent A reducing agent is something that loses electrons 77. Define the term oxidising agent An oxidising agent is something that gains electrons 78. What oxidation state do group 1 metals have? +1 79. What oxidation state to group 2 metals have? +2 80. What oxidation state do group 6 elements have? -2 81. What oxidation state do group 7 elements have? -1 82. What is the overall oxidation state of a mole- cule? 83. What is the overall oxidation state of a simple ion? 84. What is the overall oxidation state of a molecular ion? 85. What is the most common oxidation state of oxygen (with the exception of peroxides)? 86. What is the overall oxidation state of an ele- ment? 87. In a compound containing only two elements which will have the negative oxidation state? 88. What is the oxidation state of hydrogen (except for in hydrides)? 89. Is an atom oxidised or reduced if its oxidation number decreases? 0 The charge on the ion The charge on the ion -2 0 The more electronega- tive element +1 Reduced 90. Describe the function of the cytoplasm Where all of the chemi- cal reactions occur 91. Describe the function of the vesicles Transport materials in the cell and out of the cell 92. Describe the function of the nucleolus Produces ribosomes and RNA 93. Describe the function of the cell wall Provides rigidity and protection to the cell 94. Describe the function of the chloroplasts Site of photosynthesis as they contain chloro- phyll 95. Describe the function of the plasmodesmata A channel through the cell wall the allows transport of materials from one cell to another 96. Describe the function of the amyoplasts Stores starch and con- verts starch back into glucose when the plant needs energy 97. Describe the function of the vacuole Stores water and chem- icals for cell use. Also maintains turgor of cell 98. Describe the function of the tonoplasts Membrane that sur- rounds the vacuole. Protects the vacuole, isolates it from harm- ful substances and con- trols water flow in and out of the vacuole 99. Why are gram positive bacteria more suscepti- ble to antibiotics? Gram-positive have a peptidoglycan layer on the outside of the cell wall. Gram-negative bacteria have peptido- glycan between mem- branes. Penicillin works best on gram-positive bacteria by inhibiting peptidoglycan produc- tion, making the cells leaky and fragile. 100. Describe the adaptations found in a palisade cell Closely packed togeth- er Chloroplasts Large vacuole 101. Explain why the palisade cell has a large amount of chloroplasts 102. Explain why palisade cells are closely packed together To absorb lots of light for photosynthesis To form a continuous layer in the leaf 103. Explain why root hair cells have a large vacuole Contains cell sap with low water potential to encourage water into the cell 104. Explain why palisade cells have a large vacuole To maintain turgor (pushes against the cell wall to maintain rigid shape) 105. Describe the adaptations of a root hair cell Root hair shape Large surface area Large vacuole Thin cellulose walls Lots of mitochondria for active transport 106. Explain why root hair cells have an elongated section known as the root hair 107. Explain why root hair cells have thin cellulose walls Increased surface area for maximum movement of water into the cell Encourage movement of water and minerals into the cell 108. Describe the adaptations of a sperm cell Undulipodium Lots of mitochondria Shaped head contain- ing acrosome Haploid nucleus 109. Explain why a sperm cell has an undulipodium To allow the sperm to move to the egg 110. Explain why sperm cells contain large numbers of mitochondria To produce the large amounts of energy needed for movement 111. Explain why sperm cells have a shaped head To push through the protective layer of the egg cell 112. Explain why sperm cells contain acrosome in the head To digest the zona pel- lucida to allow entry into the egg cell 113. Explain why sperm cells have a haploid nucleus Contains half the genet- ic material. 114. Describe the adaptations of egg cells Contains a haploid nu- cleus Protective outer layer (zona pellucida) Corona radiata 115. Explain why egg cells have a haploid nucleus Contains half the genet- ic material 116. Explain why egg cells have a zona pellucida (protective layer) 117. Explain why egg cells have a corona radiata (two or three layers attached to the zona pellucida) Protects the cell and only allows one sperm cell to enter. Contains all of the pro- teins needed to develop the fertilised cell 118. Describe the adaptations of red blood cells No nucleus (mammals only) Biconcave shape Haemoglobin Flexible 119. Explain why red blood cells don't contain a nu- cleus 120. Explain why red blood cells have a biconcave shape 121. Explain why red blood cells contain haemoglo- bin Allows for more oxygen to be carried in the cell Increased surface area for gas exchange To bind with the oxygen in order for it to be car- ried around the body 122. Explain why red blood cells are flexible To fit through the tiny blood vessels such as capillaries 123. Describe the adaptations of neutrophils (white blood cells) 124. Explain why neutrophils (white blood cells) have a multi-lobed nucleus 125. Explain why the lysosomes found within the cy- toplasm of neutrophils (white blood cells) con- tain enzymes 126. Describe the adaptations of a lymphocyte (white blood cells) Multi-lobed nucleus Enzymes found within the lysosomes To enable the cell to squeeze through tiny gaps when travelling to the site of infection To digest engulfed pathogens T and B cells Large nucleus Smaller than neu- 127. Which white blood cell is part of the specif- ic/adaptive immune response? trophils Less cytoplasm than neutrophils Antigen receptors on surface Lymphocyte 128. Name the 3 different types of epithelial tissue Squamous epithelial tis- sue Columnar epithelial tis- sue Endothelium tissue 129. Describe squamous epithelial tissue A lining tissue that is only one cell thick. Made from squamous cells that form a smooth, flat layer. 130. Where can squamous epithelial tissue be found? 131. How can squamous epithelial tissue be dam- aged by smoking? As it is a lining tissue it can be found inside alveoli Inflammation and scar- ring of tissue Tissue gets thicker and produces more mucus Diffusion pathway is in- creased 132. What does COPD stand for? Chronic Obstructive Pulmonary Disorder 133. What symptoms can be displayed from COPD? Breathlessness Persistent coughing Phlegm build up 134. What conditions are considered part of COPD? Emphysema Chronic bronchitis 135. Describe columnar epithelial tissue Column shaped ciliated cells and goblet cells held in place by a mem- brane 136. What is meant by the term ciliated cell? A cell covered in cilia. Cilia are fine, hair like projections that 'sweep' away pathogens from the lungs 137. How does smoking affect ciliated columnar tis- sue? Toxins can paralyse or destroy cilia, lessening the 'sweeping action' overall. This leads to a build-up of mucus. 138. What is the role of the goblet cell? To produce mucus 139. How do goblet cells and ciliated cells work to- gether? Goblet cells produce mucus that sticks to pathogens, whilst cil- ia 'sweep' away the mucus containing the pathogens 140. How does smoking affect the alveoli? Toxins break the alve- oli's thin walls, leaving larger, less efficient air sacs. 141. Where is endothelial tissue found? Lining the inside of blood vessels, lymphat- ic vessels and the heart 142. Describe the structure of endothelial tissue A layer of flattened cells, one layer thick 143. What is atherosclerosis? The process of white blood cells encourag- ing the deposition of fatty substances (cho- lesterol) below the en- dothelial lining 144. What factors can increase the likelihood of ath- erosclerosis? Smoking Diet High blood pressure 145. What conditions can atherosclerosis cause? Blood clots Angina Strokes Heart attack Aneurysm and haemor- rhage 146. Name the three types of muscle tissue Skeletal Cardiac Smooth 147. What type of control is exhibited in skeletal mus- cle? 148. What type of control is exhibited in cardiac mus- cle? 149. What type of control is exhibited in smooth mus- cle? Voluntary control Involuntary control Involuntary control 150. Where can skeletal muscle be found? Attached to bones 151. Where can cardiac muscle be found? In the heart 152. Where can smooth muscle be found? In the walls of hollow or- gans such as the stom- ach and bladder 153. Put the following in order of size from largest to smallest: fibre, muscle, filaments, myofibril, bundle of fibres 154. Muscle fibres are many cells joined together. What organelles do these cells share? 155. Why do muscle cells contain many mitochon- dria? 156. Give the term used to describe the stripy bands seen within skeletal muscle under a microscope 157. Myofibril is made up of dark and light bands. What are the names given to these dark and light bands? 158. Which line is present in the middle of the A-band? Muscle, bundle of fi- bres, fibre, myofibril, fil- aments Nuclei and cytoplasm, inside which are many mitochondria and spe- cialised ER To provide large amounts of energy to the muscle for contrac- tions Striations Dark band = A-band Light band = I-band M line 159. Which line is present in the middle of the I-band? Z line 160. What is the name given to the space between two Z-lines? 161. Myofibril is made up of alternating thick and thin filaments. What are the names of these fil- aments? 162. What happens to the sarcomere during muscle contraction? Sarcomere Thick = myosin filament Thin = actin filament It shortens 163. What are the two types of skeletal muscle? Fast twitch and slow twitch 164. 164. Which sports are slow twitch muscle fibres best for? 165. Fast twitch muscles can be further divided into two sub-categories, what are they? 166. Which sports are fast twitch oxidative muscle fibres best for? 167. Which sports are fast twitch glycolytic muscle fibres best for? 168. What type of exercise are slow twitch muscles designed for? 169. What type of exercise are fast twitch muscles designed for? 170. In which type of muscle fibre is the speed of contraction slowest? 171. In which type of muscle fibre is the speed of contraction highest? 172. Describe the characteristics of slow twitch mus- cle fibres 173. Describe the characteristics of fast oxidative muscle fibres Long distance running and cycling Fast twitch oxidative muscles and fast twitch glycolytic muscles Mid-range sports such as 1500m Sprinting, short burst sports Aerobic exercise Anaerobic exercise Slow twitch Fast glycolytic twitch Less sarcoplasmic reticulum (specialised ER) More mitochondria More myoglobin A dense capillary net- work Similar to slow twitch with many mitochon- dria, myoglobin and capillaries Hydrolyse ATP faster to contract more quickly 174. Describe the characteristics of fast glycolytic twitch muscle fibres Few mitochondria and capillaries Less myoglobin Large concentration of glycogen for anaerobic respiration 175. What structures make up the nervous system? Brain, spinal cord, nerves 176. What is the scientific name for nerve cells? Neurones 177. Name the organelles of the neurone Dendrite, cytoplasm, nucleus, soma, axon, myelin sheath, axon ter- minal, Schwann cell, node of Ranvier 178. What parts of the nervous system make up the central nervous system? 179. Which parts of the nervous system make up the peripheral nervous system? Brain and spinal cord Neurones 180. Define the term 'synapse' The small gap in be- tween the axon terminal of one neurone and the dendrite of the next neu- rone 181. Define the term 'action potential The impulse passed along the axon 182. Define the term 'resting potential When the neurone is not transmitting an ac- tion potential. During this time the K+/Na+ pump is at work 183. What are the 5 sensory receptors? Touch, taste, smell, hearing, sight 184. Describe the myelin sheath A thick insulating layer around the axon 185. Describe the dendrites Highly branched fibres that conduct impulses 186. Describe the axon A long single fibre that carries nerve impulses 187. Describe the Schwann Cell A cell wrapped around the axon, forming the myelin sheath 188. Describe the nodes of Ranvier Gap in the myelin sheath where the axon is exposed 189. Describe the differences between myelinated and non-myelinated cells 190. Why do myelinated neurones transmit action po- tentials quicker than non-myelinated 191. What is the potential difference across the axon membrane during resting potential? 192. What is the potential difference across the axon membrane during an action potential? 193. What charge does the inside of an neurone have when it is polarised? Myelinated cells are longer and can transmit impulses faster down the axon Insulated by myelin sheath Impulse 'jumps' from node to node (where the sodium gates are lo- cated) -70mV +35mV Negative 194. What charge does the inside of a neurone have when it is depolarised? 195. During resting potential which ions are being moved into the cell and which ions are moved out of the cell? 196. How many sodium/potassium ions are re- moved/added in via the Na+/K+ pump? Positive Na+ removed from the cell, K+ added to the cell 3 Na+ ions removed, 2 K+ ions added 197. When does the first voltage gate open? When the axon is stim- ulated and this reaches above potential thresh- old 198. Which voltage gates are open during resting potential? 199. Which voltage gates are open during depolarisa- tion? 200. Which voltage gates are open during repolarisa- tion? None Sodium voltage gates Potassium voltage gates 201. What occurs during depolarisation? Na+ voltage gates open, Na+ floods in causing the potential difference to increase 202. What occurs during repolarisation? K+ voltage gates open, K+ floods out of the cell causing potential differ- ent to decrease 203. What is meant by the term hyper-polarisation? When the cell becomes too negative due to the loss of too many K+ 204. What is meant by the term saltatory conduction? When the impulse jumps between nodes 205. Which voltage gate opens in the synaptic bulb as the action potential reaches it? 206. What happens in the synaptic bulb as the calci- um voltage gates open? increasing the speed at which the impulse trav- els down the axon Calcium voltage gate Ca2+ floods in, stimulat- ing the vesicles to move to the membrane of the presynaptic bulb 207. Which chemical is held in the vesicles? Acetylcholine (a neuro- transmitter) 208. Define the term exocytosis The release of the acetylcholine into the synaptic cleft. This then diffuses across the synapse. 209. What causes the sodium channel to open on the postsynaptic neurone? 210. What happens to the acetylcholine after the sodium channel opens? Acetylcholine bonding to receptors on sodium voltage gate. Broken down by acetyl- cholinesterase into ethanoic acid and choline. This is then re- absorbed by the presy- naptic neurone and reformed into acetyl- choline. 211. What does EEG stand for? Electroenchephalo- gram 212. Define Oscillation A regularly repeating motion about central value 213. What is frequency? The number of whole cycles occurring in one second 214. What is the formula for frequency? f = 1/T 215. What is the Period of a wave? The time taken for one whole cycle of an oscil- lation. 216. What is Displacement of a wave? How far the quantity that is in oscillation has moved from its mean (rest) value. 217. What is the amplitude of a wave? The maximum value of displacement in the oscillation cycle. Al- ways measured from the mean position. 218. Explain a wave Waves transfer energy from one point to anoth- er without causing any net movement of mate- rial. 219. What is wavelength? The distance along the wave in its direc- tion of travel (propaga- tion) between consecu- tive points where the os- cillations are in phase. 220. What is the wave equation? v = f» 221. What is Phase Difference? The difference between two waves of the same frequency and wave- length where 360de- grees represents a sin- gle whole cycle. 222. How do particles behave in a longitudinal wave? The particles are dis- placed in the same di- rection that the wave travels. 223. How do the particles behave in a transverse wave? In a transverse wave the displacement is at right angles to the direction of the wave travel. 224. What are the two parts of a longitudinal wave. Compression (squashed) Rarefaction (spread out) 225. What are the 2 types of wave? Longitudinal And Transverse. 226. What is diffraction? Diffraction is the ten- dency of a wave to spread out in all direc- tions. 227. What is transmission of a wave? The wave energy pass- ing through an object and mostly continuing forward in the original direction. 228. What is reflection? Wave energy that bounces of a surface and has its direction of travel altered by 180de- grees 229. What is an interference pattern? A stationary pattern that can result from the su- perposition of waves travelling in different di- rections provided they are coherent. 230. What is coherence of a wave? Superposition that causes a visible inter- ference pattern. Must share the same wave- length and constant phase difference 231. What is superposition? The adding together of wave displacements that occurs when waves from 2 or more separate sources overlap. They add together. 232. What is path difference. The difference in length between 2 straight rays. 233. What happens to a light at a point of construc- tive interference? 234. What happens to light at a destructive bound- ary? The light becomes more intense. Brighter. The waves are can- celled out so there is a dark spot. 235. What is the formula for Young's slit experiment? n» =d sin ¸ 236. What is a photon? A Quantum of elec- tromagnetic radiation. Mass and charge = 0 237. What is quantum? The smallest unit that can independently ex- ist. 238. What is Quantum Theory? A combination of ideas from wave and particle mechanics 239. How is the relationship between frequency and the energy of a photon expressed? E = hf 240. What is Planck's Constant? -6.626 x 10^-34 241. Define the energy level of an electron. One of the fixed, al- lowed, values of ener- gy for an electron that is bound to an atom. 242. What is ground state? The lowest energy state possible for a given bound particle. 243. What is de-excitation of an electron? The return of an elec- tron from an outer shell to the ground state. 244. What is c, the speed of light? 3 x 10^8 m/s 245. What is E” ? The energy difference between the levels. The lost energy must equal the energy of the emit- ted photon. 246. What is a Stationary or Standing Wave? Wave motions that store energy rather than transferring energy to other locations. 247. What is a Node? Points along a station- ary wave where dis- placement amplitude is at a minimum. (ideally zero) 248. What is an Antinode? Points of maximum amplitude that occur halfway between each pair of nodes. 249. What is Resonance? The storing of energy in an oscillation or station- ary wave, the energy coming from an external source of appropriately matched frequency 250. What is forcing frequency? The frequency of wave energy from an external source that is coupled to a resonator. 251. What is Natural Frequency? A resonator has a se- ries of natural frequen- cies. Each of which cor- responds to an exact number of half wave- lengths within its bound- aries. 252. What is this formula? Wave speed formula for a standing wave 253. What is Refractive Index? The ratio of speed of light in a vacuum to its speed of light in the medium. 254. What is the formula for refractive index? The ratio of the speed of light, c, to the speed of light in the medium, v, is called the refractive index, n, of the medium. n=c/v 255. What is the Normal Line of light? The light at right angles to the surface of a trans- parent medium. 256. What is incidence of a line? The direction of the in- coming ray. 257. What is refraction? Means bending of di- rection of travel, so it describes the direction of an outgoing ray after bending. 258. What is the mathematical formula for refraction? n = c/v = sin i / sin r 259. What is Internal Reflection? When a wave that is already in an optically dense medium hits the boundary with a less dense medium the en- ergy is reflected back into the denser material 260. What is the critical angle? The angle of incidence where the angle of re- fraction is 90degrees 261. What is Total Internal Reflection? All the wave energy is internally reflected, none is lost as a refract- ed ray. 262. What is the equation for total internal reflection? 1/n = v/c = sin C => Sin C = 1/n 263. What is an optical fibre? Very long, thin cylinders of glass or plastic where light is totally internally reflected. 264. What is the benefit of optical fibre? They are a much more efficient way of transmit- ting data. 265. What is a medical use of optical fibres? Endoscopes. 266. What is an analogue signal? A signal with strength proportional to the quantity it is represent- ing. 267. What is a digital signal? Conveys in binary code a number that repre- sents the size of mea- sured quantity. 268. How fast do electromagnetic waves travel in a vacuum? All electromagnetic waves travel at the same speed in a vacu- um. 3 x 10^8 269. What is the formula for the area of a sphere? 4Àr^2 270. What is the formula for the intensity of a wave front? l = k / r^2 271. Why does the intensity of a wave front change? Because the wave is spreading out in all di- rections. 272. Name the parts of a wave. 273. Name the parts of the electromagnetic spec- trum. Peak, Trough, Wave- length, amplitude. Radio waves, Mi- crowaves, Infrared, Vis- ible light, Ultraviolet light, X-Rays, Gamma Rays