00:01
Hi, the question says that a doctor has prescribed a corrective lens of power plus 1 .5 d, d means diapter.
00:09
Find the focal length of the lens.
00:12
Is the lens diverging or converging? so, this is the question.
00:16
First of all, we will write down the power.
00:19
So the power is given p is equal to plus 1 .5b.
00:25
D means diapter, the unit of power of a lens.
00:28
Now, see, the power is in positive.
00:32
Clear? what is the relation between the focal length and the power? as we know, the focal length is equal to 1 by power.
00:43
That means the reciprocal of power.
00:45
So, p is equal to 1 by f.
00:49
F means focal length and that will be in meter.
00:53
M means meter.
00:54
What will be the unit of the focal length? that will be in meter...
