Aconverging equiconvex lens of glass of refractive index 1.5 is laid on a horizontal plane mirror. a pin coincides with its inverted image when it is 1.0m above the lens. when some liquid is placed between the lens and the mirror, the pin has to be raised by 0.55m
for coacidence to occur again. what is the refractive index of the liquid?

A5 foot by 5 foot box culvert is buried 6 feet beneath the surface of the ground. a crosssection of this very long culvert (into and out of the page) is illustrated below. assume that the soil in which the culvert is buried has the following properties: jt = 120 pcf, w = 12%, ko = 0.50, ka = 0.33, and kp = 3.00. calculate the total horizontal force per unit length of culvert (fh) felt on one of the vertical faces of the culvert.