DISPERSION OF WHITE LIGHT BY A GLASS PRISM, RAINBOW AND ATMOSPHERIC REFRACTION

 DISPERSION OF WHITE LIGHT BY A GLASS PRISM -

                                                             THE  PRISM HAS SPLIT THE INCIDENT WHITE LIGHT INTO A BEAUTIFUL BEND OF COLOURS . THE COLOURS THAT APPEAR AT TWO ENDS OF THE COLOUR BAND . THE DIFFERENT COLOUR SEEN ARE VIOLET, INDIGO BLUE GREEN YELLOW, ORANGE AND RED. THE BAND OF THE COLOURED COMPONENTS OF A LIGHT BEAM IS KNOWN AS SPECTRUM . SOME THING MAKES IT COLOUR SEPARATE FROM THE OTHER . THE SPLITTING OF THE LIGHT INTO IT SEVEN COLOUR IS KNOWN AS  THE DISPERSION .

 

ISAAC NEWTON WAS THE FIRST  WHO USE A GLASS PRISM TO GET THE SPECTRUM OF WHITE LIGHT . HE TRIED TO SPLIT OF THE COLOUR OF THE  SPECTRUM  SUNLIGHT FURTHER WITH THE HELP OF SIMILAR PRISM . HE COULD NOT GET ANY MORE COLOUR . HE THINK PUT A SECOND SIMILAR PRISM IN AN INVERTED POSITION WITH RESPECT TO THE FIRST PRISM . THIS ALLOWED ALL THE SEVEN COLOURS OF THE SPECTRUM TO PASS THROUGH THE SECOND PRISM . THIS OBSERVATION GIVE NEWTON THE IDEA THAT THE SUNLIGHT IS COMPOSED SEVEN DIFFERENT COLOURS . 

RAINBOW - 

                    THIS IS NATURAL SPECTRUM. THAT YOU CAN SEE IN SKY AFTER A RAIN SHOWER IT IS DUE TO THE DISPERSION OF SUN LIGHT BY  TINY WATER DROPLETS , PRESENT INTO ATMOSPHERE A RAIN BOW IS ALWAYS APPEARED IN DIRECTION IN OPPOSITE TO THAT OF THE SUN . THE WATER DROPLETS BEHAVE LIKE SMALL PRISM. THEY DISPERSE AND REFRACT THE INCIDENT SUNLIGHT , THAN REFLECT IT INTERNALLY ,AND FINALLY REFRACT IT AGAIN WHEN IT EMERGES OUT OF THE RAINDROP . DUE TO THE INTERNAL REFLECTION AND DISPERSION OF LIGHT ,  DIFFERENT SEVEN COLOUR REACH THE OBSERVE EYE.

 

ATMOSPHERIC REFRACTION -

                                         THE AIR JUST ABOVE THE FIRE BECOMES A HOTTER THAN AIR PRESENT FURTHER  UP . HOTTER AIR IS LIGHTER THAN THE COOLER AIR PRESENT ABOVE IT. THE HOTTER AIR CONTAINS SLIGHTLY LESS REFRACTIVE INDEX THAN THE COOLER AIR THIS RESULT WAVERING OF THINGS THIN THROUGH AIR . SUCH AN OBSERVATION SHOWS AN EFFECT ON REFRACTION OF LIGHT THROUGH THE EARTH ATMOSPHERE  ON A SMALL SCALE IN OUR SURROUNDING . TWINKLING OF STARS IS AN OPTICAL PHENOMENA  IN NATURE.

 

   TWINKLING OF STARS -      

                                    THE TWINKLING OF STARS IS BECAUSE THE ATMOSPHERIC REFRACTION OF STARLIGHT. THE STARLIGHT , AFTER ENTERING THE EARTH ATMOSPHERE UNDERGOES REFRACTION CONTINUOUSLY BEFORE IT COMES TO EARTH . THE ATMOSPHERE REFRACTION TAKE PLACE IN MEDIUM OF GRADUALLY VARYING REFRACTIVE INDEX SINCE THE ATMOSPHERE REFRACTS STARLIGHT TOWARD THE NORMAL, THE APPARENT POSITION OF THE STAR IS SLIGHTLY  DIFFERENT FROM THE REAL POSITION . THE STAR LOOKS SLIGHTLY HIGHER THAN  ITS REAL POSITION WHEN VIEWED NEAR THE HORIZON  THIS APPARENT POSITION OF THE STAR IS NOT STATIONARY BUT KEEP ON  CHANGING SLIGHTLY AND GRADUALLY , SINCE THE PHYSICAL CONDITION OF REFRACTING MEDIUM ARE NOT  STATIONARY . THE APPARENT POSITION OF STAR FLUCTUATES AND THE PATH OF BEAM OF LIGHT COMING FROM THE STAR GOES ON CHANGES SLIGHTLY . 

 ADVANCE SUNRISE AND DELAYED SUNSET -

                                                            THE SUN IS VISIBLE TO US ABOUT TWO MIN. BEFORE THE SUNRISE ABOUT TWO MIN. AFTER THE SUNSET DUE TO THE ATMOSPHERIC REFRACTION . BY SUNRISE WE MEAN THE CROSSING OF THE HORIZON BY SUN. 

THE DIFFERENCE TIME  BETWEEN SUNSET THE APPARENT SUNSET IS ABOUT TWO MIN. THE APPARENT FLATTING OF THE DISC OF THE SUN AT SUNRISE AND SUNSET IS ALSO BECAUSE OF   SAME PHENOMENON  .