Calculating the ratio of charges in Leyden Jar

[bksree]

Hello
In Walter Lewin's lecture while explaining the Leyden jar he says that the charge on the glass is 12 times more than that in the air gap.
How is this obtained ?

Basically there are 2 metal containers separated by a glass sheet. The air gap between the outer conductor and glass is 1 mm, the thickness of glass is 3 mm and the airgap between the glass and the inner conductor is 1 mm.
The electric fields in the air gap and glass are worked out to be as below :

(i)air gap of 1 mm thickness and electric field of 3*10^6 V/m in it
(ii)adjacent to air gap is : glass sheet of 3 mm thickness and electric field of 8*10^6 V/m
(iii) another air gap of 1 mm thickness and electric field of 3*10^6 V/m in it

Since Q is proportional to AE, shouldn't the ratio of charge on glass to charge on metal be 8/3 ?

TIA

 

[Vailanor]

No, the ratio of charge on the glass to the charge on the metal is not 8/3. This is because the two air gaps have the same electric field. Therefore, the ratio of charge on the glass to the charge on the metal is 12.