0:03 [Music]
0:06 these were the two laws of refraction of
0:09 light we saw in a previous video the
0:11 Snell's law tells us that this ratio is
0:14 constant and is equal to the refractive
0:16 index of medium 2 with respect to medium
0:20 1 and it is also equal to the ratio of
0:23 speed of light in medium 1 to the speed
0:26 of light in medium 2 and that is the
0:28 same as the ratio of the absolute
0:31 refractive index of medium 2 to the
0:34 absolute refractive index of medium 1
0:36 let's try to solve a simple example
0:39 based on this here is the question on
0:48 your screen go through it carefully we
0:50 are given the refractive index of glass
0:53 with respect to air as 1.50
0:56 here air is the incident medium and
0:59 glass is the refractive medium let us
1:02 take medium one as air and medium two as
1:06 glass so n - 1 is equal to one point
1:11 five zero but what is n - 1 equal to yes
1:14 it's equal to speed of light in medium 1
1:18 over the speed of light in medium 2 here
1:21 V 1 is speed of light in air and V 2 is
1:25 a speed of light in glass but we aren't
1:27 given any of the two values we want to
1:29 find out the speed of light in glass and
1:32 for that we need the speed of light in
1:38 air we can write V 2 as V 1 over 1.5 the
1:41 value of speed of light in air is very
1:43 close to the value of speed of light in
1:46 vacuum hence we can substitute this
1:49 value in place of speed of light in air
1:52 after doing a bit of math we will get
1:54 the speed of light in glass as 2 times
1:57 10 to the power 8 meters per second
2:01 don't forget the unit's we see that the
2:04 speed of light in glass is lesser in the
2:06 next video we will talk about an
2:08 important optical device which is very
2:09 widely used [Music]
