A monochromatic beam of light travels through air of refractive index na and strikes a liquid of refractive index ny at an angle of incidence as shown in the figure below. At the bottom of the tank which contains the liquid is a plane mirror at angle o to the horizontal. The tank can be considered infinitely long. Beyond a certain value of the light no longer leaves the tank after the first reflection in the mirror. Find the value of for this case given o= 10, na = 1 and n = . You may wish to use the larger diagram below to draw a ray diagram. [5]