Liquid-detecting prism devices may be used in a washing machine or other liquid-containing devices. If no liquid covers the prism's hypotenuse, total internal refletion from the light source produces a large signal in the light sensor. If liquid covers the hypotenuse, some light escapes from the prism into the liquid and the light sensor's signal decreases. Thus, a large signal from the light sensor indicates the absence of liquid in the resevoir. If this device is designed to detect the presence of water, determine the allowable range for the prism's index of refraction n.
n of water = 1.33

The prism is a 45/45/90 triangle affixed with the hypotenuse attatched to a rectangular tub of water. The light source and light sensor are underneath the prism on opposing sides.