°®°®Ð¡ËµÍø > ÆäËûµç×ÓÊé > meteorology >

µÚ16ÕÂ

meteorology-µÚ16ÕÂ

С˵£º meteorology ×ÖÊý£º ÿҳ3500×Ö

°´¼üÅÌÉÏ·½Ïò¼ü ¡û »ò ¡ú ¿É¿ìËÙÉÏÏ·­Ò³£¬°´¼üÅÌÉ쵀 Enter ¼ü¿É»Øµ½±¾ÊéĿ¼ҳ£¬°´¼üÅÌÉÏ·½Ïò¼ü ¡ü ¿É»Øµ½±¾Ò³¶¥²¿£¡
¡ª¡ª¡ª¡ªÎ´ÔĶÁÍꣿ¼ÓÈëÊéÇ©ÒѱãÏ´μÌÐøÔĶÁ£¡





¡¡¡¡Haloes¡¡are¡¡formed¡¡round¡¡stars¡¡for¡¡the¡¡same¡¡reasons£»¡¡but¡¡they¡¡are¡¡not



prognostic¡¡in¡¡the¡¡same¡¡way¡¡because¡¡the¡¡condensation¡¡they¡¡imply¡¡is¡¡so



insignificant¡¡as¡¡to¡¡be¡¡barren¡£







¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡4







¡¡¡¡We¡¡have¡¡already¡¡stated¡¡that¡¡the¡¡rainbow¡¡is¡¡a¡¡reflection£º¡¡we¡¡have¡¡now



to¡¡explain¡¡what¡¡sort¡¡of¡¡reflection¡¡it¡¡is£»¡¡to¡¡describe¡¡its¡¡various



concomitants£»¡¡and¡¡to¡¡assign¡¡their¡¡causes¡£



¡¡¡¡Sight¡¡is¡¡reflected¡¡from¡¡all¡¡smooth¡¡surfaces£»¡¡such¡¡as¡¡are¡¡air¡¡and



water¡¡among¡¡others¡£¡¡Air¡¡must¡¡be¡¡condensed¡¡if¡¡it¡¡is¡¡to¡¡act¡¡as¡¡a¡¡mirror£»



though¡¡it¡¡often¡¡gives¡¡a¡¡reflection¡¡even¡¡uncondensed¡¡when¡¡the¡¡sight



is¡¡weak¡£¡¡Such¡¡was¡¡the¡¡case¡¡of¡¡a¡¡man¡¡whose¡¡sight¡¡was¡¡faint¡¡and



indistinct¡£¡¡He¡¡always¡¡saw¡¡an¡¡image¡¡in¡¡front¡¡of¡¡him¡¡and¡¡facing¡¡him¡¡as



he¡¡walked¡£¡¡This¡¡was¡¡because¡¡his¡¡sight¡¡was¡¡reflected¡¡back¡¡to¡¡him¡£¡¡Its



morbid¡¡condition¡¡made¡¡it¡¡so¡¡weak¡¡and¡¡delicate¡¡that¡¡the¡¡air¡¡close¡¡by



acted¡¡as¡¡a¡¡mirror£»¡¡just¡¡as¡¡distant¡¡and¡¡condensed¡¡air¡¡normally¡¡does£»



and¡¡his¡¡sight¡¡could¡¡not¡¡push¡¡it¡¡back¡£¡¡So¡¡promontories¡¡in¡¡the¡¡sea



'loom'¡¡when¡¡there¡¡is¡¡a¡¡south¡­east¡¡wind£»¡¡and¡¡everything¡¡seems¡¡bigger£»



and¡¡in¡¡a¡¡mist£»¡¡too£»¡¡things¡¡seem¡¡bigger£º¡¡so£»¡¡too£»¡¡the¡¡sun¡¡and¡¡the¡¡stars



seem¡¡bigger¡¡when¡¡rising¡¡and¡¡setting¡¡than¡¡on¡¡the¡¡meridian¡£¡¡But¡¡things



are¡¡best¡¡reflected¡¡from¡¡water£»¡¡and¡¡even¡¡in¡¡process¡¡of¡¡formation¡¡it



is¡¡a¡¡better¡¡mirror¡¡than¡¡air£»¡¡for¡¡each¡¡of¡¡the¡¡particles£»¡¡the¡¡union¡¡of



which¡¡constitutes¡¡a¡¡raindrop£»¡¡is¡¡necessarily¡¡a¡¡better¡¡mirror¡¡than



mist¡£¡¡Now¡¡it¡¡is¡¡obvious¡¡and¡¡has¡¡already¡¡been¡¡stated¡¡that¡¡a¡¡mirror¡¡of



this¡¡kind¡¡renders¡¡the¡¡colour¡¡of¡¡an¡¡object¡¡only£»¡¡but¡¡not¡¡its¡¡shape¡£



Hence¡¡it¡¡follows¡¡that¡¡when¡¡it¡¡is¡¡on¡¡the¡¡point¡¡of¡¡raining¡¡and¡¡the¡¡air



in¡¡the¡¡clouds¡¡is¡¡in¡¡process¡¡of¡¡forming¡¡into¡¡raindrops¡¡but¡¡the¡¡rain



is¡¡not¡¡yet¡¡actually¡¡there£»¡¡if¡¡the¡¡sun¡¡is¡¡opposite£»¡¡or¡¡any¡¡other¡¡object



bright¡¡enough¡¡to¡¡make¡¡the¡¡cloud¡¡a¡¡mirror¡¡and¡¡cause¡¡the¡¡sight¡¡to¡¡be



reflected¡¡to¡¡the¡¡object¡¡then¡¡the¡¡reflection¡¡must¡¡render¡¡the¡¡colour



of¡¡the¡¡object¡¡without¡¡its¡¡shape¡£¡¡Since¡¡each¡¡of¡¡the¡¡mirrors¡¡is¡¡so¡¡small



as¡¡to¡¡be¡¡invisible¡¡and¡¡what¡¡we¡¡see¡¡is¡¡the¡¡continuous¡¡magnitude¡¡made¡¡up



of¡¡them¡¡all£»¡¡the¡¡reflection¡¡necessarily¡¡gives¡¡us¡¡a¡¡continuous



magnitude¡¡made¡¡up¡¡of¡¡one¡¡colour£»¡¡each¡¡of¡¡the¡¡mirrors¡¡contributing



the¡¡same¡¡colour¡¡to¡¡the¡¡whole¡£¡¡We¡¡may¡¡deduce¡¡that¡¡since¡¡these



conditions¡¡are¡¡realizable¡¡there¡¡will¡¡be¡¡an¡¡appearance¡¡due¡¡to



reflection¡¡whenever¡¡the¡¡sun¡¡and¡¡the¡¡cloud¡¡are¡¡related¡¡in¡¡the¡¡way



described¡¡and¡¡we¡¡are¡¡between¡¡them¡£¡¡But¡¡these¡¡are¡¡just¡¡the¡¡conditions



under¡¡which¡¡the¡¡rainbow¡¡appears¡£¡¡So¡¡it¡¡is¡¡clear¡¡that¡¡the¡¡rainbow¡¡is



a¡¡reflection¡¡of¡¡sight¡¡to¡¡the¡¡sun¡£



¡¡¡¡So¡¡the¡¡rainbow¡¡always¡¡appears¡¡opposite¡¡the¡¡sun¡¡whereas¡¡the¡¡halo¡¡is



round¡¡it¡£¡¡They¡¡are¡¡both¡¡reflections£»¡¡but¡¡the¡¡rainbow¡¡is



distinguished¡¡by¡¡the¡¡variety¡¡of¡¡its¡¡colours¡£¡¡The¡¡reflection¡¡in¡¡the¡¡one



case¡¡is¡¡from¡¡water¡¡which¡¡is¡¡dark¡¡and¡¡from¡¡a¡¡distance£»¡¡in¡¡the¡¡other



from¡¡air¡¡which¡¡is¡¡nearer¡¡and¡¡lighter¡¡in¡¡colour¡£¡¡White¡¡light¡¡through



a¡¡dark¡¡medium¡¡or¡¡on¡¡a¡¡dark¡¡surface¡¡£¨it¡¡makes¡¡no¡¡difference£©¡¡looks¡¡red¡£



We¡¡know¡¡how¡¡red¡¡the¡¡flame¡¡of¡¡green¡¡wood¡¡is£º¡¡this¡¡is¡¡because¡¡so¡¡much



smoke¡¡is¡¡mixed¡¡with¡¡the¡¡bright¡¡white¡¡firelight£º¡¡so£»¡¡too£»¡¡the¡¡sun



appears¡¡red¡¡through¡¡smoke¡¡and¡¡mist¡£¡¡That¡¡is¡¡why¡¡in¡¡the¡¡rainbow



reflection¡¡the¡¡outer¡¡circumference¡¡is¡¡red¡¡£¨the¡¡reflection¡¡being¡¡from



small¡¡particles¡¡of¡¡water£©£»¡¡but¡¡not¡¡in¡¡the¡¡case¡¡of¡¡the¡¡halo¡£¡¡The



other¡¡colours¡¡shall¡¡be¡¡explained¡¡later¡£¡¡Again£»¡¡a¡¡condensation¡¡of



this¡¡kind¡¡cannot¡¡persist¡¡in¡¡the¡¡neighbourhood¡¡of¡¡the¡¡sun£º¡¡it¡¡must



either¡¡turn¡¡to¡¡rain¡¡or¡¡be¡¡dissolved£»¡¡but¡¡opposite¡¡to¡¡the¡¡sun¡¡there



is¡¡an¡¡interval¡¡during¡¡which¡¡the¡¡water¡¡is¡¡formed¡£¡¡If¡¡there¡¡were¡¡not



this¡¡distinction¡¡haloes¡¡would¡¡be¡¡coloured¡¡like¡¡the¡¡rainbow¡£¡¡Actually



no¡¡complete¡¡or¡¡circular¡¡halo¡¡presents¡¡this¡¡colour£»¡¡only¡¡small¡¡and



fragmentary¡¡appearances¡¡called¡¡'rods'¡£¡¡But¡¡if¡¡a¡¡haze¡¡due¡¡to¡¡water¡¡or



any¡¡other¡¡dark¡¡substance¡¡formed¡¡there¡¡we¡¡should¡¡have¡¡had£»¡¡as¡¡we



maintain£»¡¡a¡¡complete¡¡rainbow¡¡like¡¡that¡¡which¡¡we¡¡do¡¡find¡¡lamps¡£¡¡A



rainbow¡¡appears¡¡round¡¡these¡¡in¡¡winter£»¡¡generally¡¡with¡¡southerly¡¡winds¡£



Persons¡¡whose¡¡eyes¡¡are¡¡moist¡¡see¡¡it¡¡most¡¡clearly¡¡because¡¡their¡¡sight



is¡¡weak¡¡and¡¡easily¡¡reflected¡£¡¡It¡¡is¡¡due¡¡to¡¡the¡¡moistness¡¡of¡¡the¡¡air



and¡¡the¡¡soot¡¡which¡¡the¡¡flame¡¡gives¡¡off¡¡and¡¡which¡¡mixes¡¡with¡¡the¡¡air



and¡¡makes¡¡it¡¡a¡¡mirror£»¡¡and¡¡to¡¡the¡¡blackness¡¡which¡¡that¡¡mirror



derives¡¡from¡¡the¡¡smoky¡¡nature¡¡of¡¡the¡¡soot¡£¡¡The¡¡light¡¡of¡¡the¡¡lamp



appears¡¡as¡¡a¡¡circle¡¡which¡¡is¡¡not¡¡white¡¡but¡¡purple¡£¡¡It¡¡shows¡¡the



colours¡¡of¡¡the¡¡rainbow£»¡¡but¡¡because¡¡the¡¡sight¡¡that¡¡is¡¡reflected¡¡is¡¡too



weak¡¡and¡¡the¡¡mirror¡¡too¡¡dark£»¡¡red¡¡is¡¡absent¡£¡¡The¡¡rainbow¡¡that¡¡is



seen¡¡when¡¡oars¡¡are¡¡raised¡¡out¡¡of¡¡the¡¡sea¡¡involves¡¡the¡¡same¡¡relative



positions¡¡as¡¡that¡¡in¡¡the¡¡sky£»¡¡but¡¡its¡¡colour¡¡is¡¡more¡¡like¡¡that¡¡round



the¡¡lamps£»¡¡being¡¡purple¡¡rather¡¡than¡¡red¡£¡¡The¡¡reflection¡¡is¡¡from¡¡very



small¡¡particles¡¡continuous¡¡with¡¡one¡¡another£»¡¡and¡¡in¡¡this¡¡case¡¡the



particles¡¡are¡¡fully¡¡formed¡¡water¡£¡¡We¡¡get¡¡a¡¡rainbow£»¡¡too£»¡¡if¡¡a¡¡man



sprinkles¡¡fine¡¡drops¡¡in¡¡a¡¡room¡¡turned¡¡to¡¡the¡¡sun¡¡so¡¡that¡¡the¡¡sun¡¡is



shining¡¡in¡¡part¡¡of¡¡the¡¡room¡¡and¡¡throwing¡¡a¡¡shadow¡¡in¡¡the¡¡rest¡£¡¡Then¡¡if



one¡¡man¡¡sprinkles¡¡in¡¡the¡¡room£»¡¡another£»¡¡standing¡¡outside£»¡¡sees¡¡a



rainbow¡¡where¡¡the¡¡sun's¡¡rays¡¡cease¡¡and¡¡make¡¡the¡¡shadow¡£¡¡Its¡¡nature¡¡and



colour¡¡is¡¡like¡¡that¡¡from¡¡the¡¡oars¡¡and¡¡its¡¡cause¡¡is¡¡the¡¡same£»¡¡for¡¡the



sprinkling¡¡hand¡¡corresponds¡¡to¡¡the¡¡oar¡£



¡¡¡¡That¡¡the¡¡colours¡¡of¡¡the¡¡rainbow¡¡are¡¡those¡¡we¡¡described¡¡and¡¡how¡¡the



other¡¡colours¡¡come¡¡to¡¡appear¡¡in¡¡it¡¡will¡¡be¡¡clear¡¡from¡¡the¡¡following



considerations¡£¡¡We¡¡must¡¡recognize£»¡¡as¡¡we¡¡have¡¡said£»¡¡and¡¡lay¡¡down£º



first£»¡¡that¡¡white¡¡colour¡¡on¡¡a¡¡black¡¡surface¡¡or¡¡seen¡¡through¡¡a¡¡black



medium¡¡gives¡¡red£»¡¡second£»¡¡that¡¡sight¡¡when¡¡strained¡¡to¡¡a¡¡distance



becomes¡¡weaker¡¡and¡¡less£»¡¡third£»¡¡that¡¡black¡¡is¡¡in¡¡a¡¡sort¡¡the¡¡negation



of¡¡sight£º¡¡an¡¡object¡¡is¡¡black¡¡because¡¡sight¡¡fails£»¡¡so¡¡everything¡¡at¡¡a



distance¡¡looks¡¡blacker£»¡¡because¡¡sight¡¡does¡¡not¡¡reach¡¡it¡£¡¡The¡¡theory¡¡of



these¡¡matters¡¡belongs¡¡to¡¡the¡¡account¡¡of¡¡the¡¡senses£»¡¡which¡¡are¡¡the



proper¡¡subjects¡¡of¡¡such¡¡an¡¡inquiry£»¡¡we¡¡need¡¡only¡¡state¡¡about¡¡them¡¡what



is¡¡necessary¡¡for¡¡us¡£¡¡At¡¡all¡¡events£»¡¡that¡¡is¡¡the¡¡reason¡¡why¡¡distant



objects¡¡and¡¡objects¡¡seen¡¡in¡¡a¡¡mirror¡¡look¡¡darker¡¡and¡¡smaller¡¡and



smoother£»¡¡why¡¡the¡¡reflection¡¡of¡¡clouds¡¡in¡¡water¡¡is¡¡darker¡¡than¡¡the



clouds¡¡themselves¡£¡¡This¡¡latter¡¡is¡¡clearly¡¡the¡¡case£º¡¡the¡¡reflection



diminishes¡¡the¡¡sight¡¡that¡¡reaches¡¡them¡£¡¡It¡¡makes¡¡no¡¡difference¡¡whether



the¡¡change¡¡is¡¡in¡¡the¡¡object¡¡seen¡¡or¡£¡¡in¡¡the¡¡sight£»¡¡the¡¡result¡¡being¡¡in



either¡¡case¡¡the¡¡same¡£¡¡The¡¡following¡¡fact¡¡further¡¡is¡¡worth¡¡noticing¡£



When¡¡there¡¡is¡¡a¡¡cloud¡¡near¡¡the¡¡sun¡¡and¡¡we¡¡look¡¡at¡¡it¡¡does¡¡not¡¡look



coloured¡¡at¡¡all¡¡but¡¡white£»¡¡but¡¡when¡¡we¡¡look¡¡at¡¡the¡¡same¡¡cloud¡¡in¡¡water



it¡¡shows¡¡a¡¡trace¡¡of¡¡rainbow¡¡colouring¡£¡¡Clearly£»¡¡then£»¡¡when¡¡sight¡¡is



reflected¡¡it¡¡is¡¡weakened¡¡and£»¡¡as¡¡it¡¡makes¡¡dark¡¡look¡¡darker£»¡¡so¡¡it



makes¡¡white¡¡look¡¡less¡¡white£»¡¡changing¡¡it¡¡and¡¡bringing¡¡it¡¡nearer¡¡to



black¡£¡¡When¡¡the¡¡sight¡¡is¡¡relatively¡¡strong¡¡the¡¡change¡¡is¡¡to¡¡red£»¡¡the



next¡¡stage¡¡is¡¡green£»¡¡and¡¡a¡¡further¡¡degree¡¡of¡¡weakness¡¡gives¡¡violet¡£¡¡No



further¡¡change¡¡is¡¡visible£»¡¡but¡¡three¡¡completes¡¡the¡¡series¡¡of¡¡colours



£¨as¡¡we¡¡find¡¡three¡¡does¡¡in¡¡most¡¡other¡¡things£©£»¡¡and¡¡the¡¡change¡¡into



the¡¡rest¡¡is¡¡imperceptible¡¡to¡¡sense¡£¡¡Hence¡¡also¡¡the¡¡rainbow¡¡appears



with¡¡three¡¡colours£»¡¡this¡¡is¡¡true¡¡of¡¡each¡¡of¡¡the¡¡two£»¡¡but¡¡in¡¡a¡¡contrary



way¡£¡¡The¡¡outer¡¡band¡¡of¡¡the¡¡primary¡¡rainbow¡¡is¡¡red£º¡¡for¡¡the¡¡largest



band¡¡reflects¡¡most¡¡sight¡¡to¡¡the¡¡sun£»¡¡and¡¡the¡¡outer¡¡band¡¡is¡¡largest¡£



The¡¡middle¡¡band¡¡and¡¡the¡¡third¡¡go¡¡on¡¡the¡¡same¡¡principle¡£¡¡So¡¡if¡¡the



principles¡¡we¡¡laid¡¡down¡¡about¡¡the¡¡appearance¡¡of¡¡colours¡¡are¡¡true¡¡the



rainbow¡¡necessarily¡¡has¡¡three¡¡colours£»¡¡and¡¡these¡¡three¡¡and¡¡no



others¡£¡¡The¡¡appearance¡¡of¡¡yellow¡¡is¡¡due¡¡to¡¡contrast£»¡¡for¡¡the¡¡red¡¡is



whitened¡¡by¡¡its¡¡juxtaposition¡¡with¡¡green¡£¡¡We¡¡can¡¡see¡¡this¡¡from¡¡the



fact¡¡that¡¡the¡¡rainbow¡¡is¡¡purest¡¡when¡¡the¡¡cloud¡¡is¡¡blackest£»¡¡and¡¡then



the¡¡red¡¡shows¡¡most¡¡yellow¡£¡¡£¨Yellow¡¡in¡¡the¡¡rainbow¡¡comes¡¡between¡¡red



and¡¡green¡££©¡¡So¡¡the¡¡whole¡¡of¡¡the¡¡red¡¡shows¡¡white¡¡by¡¡contrast¡¡with¡¡the



blackness¡¡of¡¡the¡¡cloud¡¡around£º¡¡for¡¡it¡¡is¡¡white¡¡compared¡¡to¡¡the¡¡cloud



and¡¡the¡¡green¡£¡¡Again£»¡¡when¡¡the¡¡rainbow¡¡is¡¡fading¡¡away¡¡and¡¡the¡¡red¡¡is



dissolving£»¡¡the¡¡white¡¡cloud¡¡is¡¡brought¡¡into¡¡contact¡¡with¡¡the¡¡green¡¡and



becomes¡¡yellow¡£¡¡But¡¡the¡¡moon¡¡rainbow¡¡affords¡¡the¡¡best¡¡instance¡¡of¡¡this



colour¡¡contrast¡£¡¡It¡¡looks¡¡quite¡¡white£º¡¡this¡¡is¡¡because¡¡it¡¡appears¡¡on



the¡¡dark¡¡cloud¡¡and¡¡at¡¡night¡£¡¡So£»¡¡just¡¡as¡¡fire¡¡is¡¡intensified¡¡by



added¡¡fire£»¡¡black¡¡beside¡¡black¡¡makes¡¡that¡¡which¡¡is¡¡in¡¡some¡¡degree



white¡¡look¡¡quite¡¡white¡£¡¡Bright¡¡dyes¡¡too¡¡show¡¡the¡¡effect¡¡of¡¡contrast¡£



In¡¡woven¡¡and¡¡embroidered¡¡stuffs¡¡the¡¡appearance¡¡of¡¡colours¡¡is



profoundly¡¡affected¡¡by¡¡their¡¡juxtaposition¡¡with¡¡one¡¡another¡¡£¨purple£»



for¡¡instance£»¡¡appears¡¡different¡¡on¡¡white¡¡and¡¡on¡¡black¡¡wool£©£»¡¡and



also¡¡by¡¡differences¡¡of¡¡illumination¡£¡¡Thus¡¡embroiderers¡¡say¡¡that¡¡they



often¡¡make¡¡mistakes¡¡in¡¡their¡¡colours¡¡when¡¡they¡¡work¡¡by¡¡lamplight£»



and¡¡use¡¡the¡¡wrong¡¡ones¡£



¡¡¡¡We¡¡have¡¡now¡¡shown¡¡why¡¡the¡¡rainbow¡¡has¡¡three¡¡colours¡¡and¡¡that¡¡these



are¡¡its¡¡only¡¡colours¡£¡¡The¡¡same¡¡cause¡¡explains¡¡the¡¡double¡¡rainbow¡¡and



the¡¡faintness¡¡of¡¡the¡¡colours¡¡in¡¡the¡¡outer¡¡one¡¡and¡¡their¡¡inverted



order¡£¡¡When¡¡sight¡¡is¡¡strained¡¡to¡¡a¡¡great¡¡distance¡¡the¡¡appearance¡¡of



the¡¡distant¡¡object¡¡is¡¡affected¡¡in¡¡a¡¡certain¡¡way£º¡¡and¡¡the¡¡same¡¡thing



holds¡¡good¡¡here¡£¡¡So¡¡the¡¡reflection¡¡from¡¡the¡¡outer¡¡rainbow¡¡is¡¡weaker



because¡¡it¡¡takes¡¡place¡¡from¡¡a¡¡greater¡¡distance¡¡and¡¡less¡¡of¡¡it



reaches¡¡the¡¡sun£»¡¡and¡¡so¡¡the¡¡colours¡¡seen¡¡are¡¡fainter¡£¡¡Their¡¡order¡¡is



reversed¡¡because¡¡more¡¡reflection¡¡reaches¡¡the¡¡sun¡¡from¡¡the¡¡smaller£»



inner¡¡band¡£¡¡For¡¡that¡¡reflection¡¡is¡¡nearer¡¡to¡¡our¡¡sight¡¡which¡¡is



reflected¡¡from¡¡the¡¡band¡¡which¡¡is¡¡nearest¡¡to¡¡the¡¡primary¡¡rainbow¡£¡¡Now



the¡¡smallest¡¡band¡¡in¡¡the¡¡outer¡¡rainbow¡¡is¡¡that¡¡which¡¡is¡¡nearest£»¡¡and



so¡¡it¡¡will¡¡be¡¡red£»¡¡and¡¡the¡¡second¡¡and¡¡the¡¡third¡¡will¡¡follow¡¡the¡¡same



principle¡£¡¡Let¡¡B¡¡be¡¡the¡¡outer¡¡rainbow£»¡¡A¡¡the¡¡inner¡¡one£»¡¡let¡¡R¡¡stand



for¡¡the¡¡red¡¡colour£»¡¡G¡¡for¡¡green£»¡¡V¡¡for¡¡violet£»¡¡yellow¡¡appears¡¡at¡¡the



point¡¡Y¡£¡¡Three¡¡rainbows¡¡or¡¡more¡¡are¡¡not¡¡found¡¡because¡¡even¡¡the



second¡¡is¡¡fainter£»¡¡so¡¡that¡¡the¡¡third¡¡reflection¡¡can¡¡have¡¡no¡¡strength



whatever¡¡and¡¡cannot¡¡reach¡¡the¡¡sun¡¡at¡¡all¡£¡¡£¨See¡¡diagram¡££©







¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡5







¡¡¡¡The¡¡rainbow¡¡can¡¡never¡¡be¡¡a¡¡circle¡¡nor¡¡a¡¡segment¡¡of¡¡a¡¡circle



greater¡¡than¡¡a¡¡semicircle¡£¡¡The¡¡consideration¡¡of¡¡the¡¡diagram¡¡will¡¡prove



this¡¡and¡¡the¡¡other¡¡properties¡¡of¡¡the¡¡rainbow¡£¡¡£¨See¡¡diagram¡££©



¡¡¡¡Let¡¡A¡¡be¡¡a¡¡hemisphere¡¡resting¡¡on¡¡the¡¡circle¡¡of¡¡the¡¡horizon£»¡¡let



its¡¡centre¡¡be¡¡K¡¡and¡¡let¡¡H¡¡be¡¡another¡¡point¡¡appearing¡¡on¡¡the¡¡horizon¡£



Then£»¡¡if¡¡the¡¡lines¡¡that¡¡fall¡¡in¡¡a¡¡cone¡¡from¡¡K¡¡have¡¡HK¡¡as¡¡their¡¡axis£»



and£»¡¡K¡¡and¡¡M¡¡being¡¡joined£»¡¡the¡¡lines¡¡KM¡¡are¡¡reflected¡¡from¡¡the



hemisphere¡¡to¡¡H¡¡over¡¡the¡¡greater¡¡angle£»¡¡the¡¡lines¡¡from¡¡K¡¡will¡¡fall



on¡¡the¡¡circumference¡¡of¡¡a¡¡circle¡£¡¡If¡¡the¡¡reflection¡¡takes¡¡place¡¡when



the¡¡luminous¡¡body¡¡is¡¡rising¡¡or¡¡setting¡¡the¡¡segment¡¡of¡¡the¡¡circ

·µ»ØĿ¼ ÉÏÒ»Ò³ ÏÂÒ»Ò³ »Øµ½¶¥²¿ ÔÞ£¨0£© ²È£¨0£©

Äã¿ÉÄÜϲ»¶µÄ