A microscope is focused on a mark on a table, when the mark is covered by a plate of glass 2m thick, the microscope has to be raised 0.67cm for the mark to be once more in focus. Calculate the refractive index.
1.50
1.68
2.58
1.82
Explanation
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D=t(n-1)/n
let
D= displacement
t= THICKNESS
n= refractive index
0.67= 2(n-1)/n
factorize out
0.67=2n-2/n
cross multiply
0.67n=2n-2
CLT
2=2n-0. 67n
2=1.33n
divide both sides by 1.33
n=2/1.33
n= 1.5
Though there's an mistake in the unit I guess the best thing to do is to overlook the mistake.
Refractive index=Real depth/Apparent depth.
In the question,we were given our real depth as 2m we weren't given our apparent depth but we're given apparent displacement to be 0.67m.
Recall that Apparent displacement=Real depth - Apparent depth.
Substuting we have;
0.67=2-x
(The x represent the apparent depth which is unknown)
X=2-0.67
X=1.33m
Refractive index=2/1.33
Refractive index=1.50
Just hope it's understandable
this question
thought the units have to be uniform
in the question I'm seeing cm and m
someone pls correct me 
