a:9:{i:0;a:4:{s:4:"html";s:2:"Hi";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:16:24";s:4:"flow";i:0;}i:1;a:4:{s:4:"html";s:12:"Good evening";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:16:37";s:4:"flow";i:1;}i:2;a:4:{s:4:"html";s:6:"Hi sir";s:6:"userId";i:31474201;s:7:"created";s:19:"2019-03-11 15:16:34";s:4:"flow";i:2;}i:3;a:4:{s:4:"html";s:70:"Refractive index = speed of light in vaccum / speed of light in medium";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:17:24";s:4:"flow";i:3;}i:4;a:4:{s:4:"html";s:16:"Use this formula";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:17:22";s:4:"flow";i:4;}i:5;a:4:{s:4:"html";s:42:"So
4/3 = speed of light in vaccum/ 2*10^8";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:18:05";s:4:"flow";i:5;}i:6;a:4:{s:4:"html";s:39:"Speed of light in vaccum= 2.67*10^8 m/s";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:18:58";s:4:"flow";i:6;}i:7;a:4:{s:4:"html";s:50:"Similarly
3/2 = 2.67*10^8/speed of light in water";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:19:44";s:4:"flow";i:7;}i:8;a:4:{s:4:"html";s:19:"Are you able to get";s:6:"userId";i:26324805;s:7:"created";s:19:"2019-03-11 15:19:48";s:4:"flow";i:8;}}