Three glasses are placed by a waiter on a light-weight tray. The first glass has a mass of M1 = 575 g and is located R1 = 18 cm from the center of the tray at an angle θ1 = 45 degrees above the positive x-axis. The second glass has a mass of M2 = 450 g and is located R2 = 24 cm from the center of the tray at an angle θ2 = 55 degrees below the positive x-axis. The third glass has a mass of M3 = 275 g and is located R3 = 19 cm from the center of the tray at an angle θ3 = 45 degrees above the negative x-axis. A fourth glass of mass M4 = 850 g is to be placed on the tray so that the center of mass is located at the center of the tray.

reserve is the answer

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.