Two parallel sheets of glass (?_r = 8.5) mounted vertically are separated by a uniform air gap between their inner surface. The sheets, properly sealed, are immersed in oil (?_r = 3.0) as shown in figure. A uniform electric field of strength 2000 V/m in the horizontal direction exists in the oil. Calculate the magnitude and direction of the electric field in the glass and in the enclosed air gap when?

(a) The field is normal to the glass surfaces, and?

(b) The field in the oil makes an angle of 75? with a normal to the glass surfaces. Ignore edge effects.

glass oil oil air