Final answer:
The ratio of the intensity of light reflected from the back surface of the glass to the intensity reflected from the front surface, I2/I1, is 1 given normal incident and assuming no absorption or other losses within the glass.
Step-by-step explanation:
The question concerns the principles of reflection and refraction in the context of optic physics. We are looking for the ratio of the intensity of light reflected from the back surface of a piece of glass (I2) to the intensity of light reflected from the front surface (I1). The index of refraction for the glass is given as n = 1.890, and it is specified that the light is incident normally on the surface, which indicates an incident angle of 0 degrees.
To analyze the reflection at each surface, we would normally use Fresnel's equations, which describe how light behaves at the interface between two media with different indices of refraction. However, given that the incident light is normal to the surface, the reflectance R at each surface is given by:
R = ((n - 1)/(n + 1))^2
Thus, I1 and I2 are proportional to the reflectance at the respective front and back surfaces. Since the question assumes the same physical conditions for both reflections, I1 should be equal to I2, and therefore the ratio I2/I1 is 1, assuming no absorption or additional loss mechanisms within the glass.