A submarine is observed to rise from a real depth off 80 m to 60 m in water. calculate the change in apparent depth. [Refraction index of water (4)/3]

The apparent depth of an object in water is the depth at which it appears to be when viewed from above the water's surface. The apparent depth of an object is affected by the refractive index of water, which is a measure of how much light is bent as it passes from one medium to another. When a submarine rises from a real depth of 80 m to 60 m, its apparent depth changes because the light rays from the submarine bend as they pass from water to air, causing the submarine to appear to be at a different depth than it actually is. To calculate the change in apparent depth, we need to use the formula: Change in apparent depth = real depth x (refractive index of water - 1) Plugging in the values, we get: Change in apparent depth = 80m x (4/3 - 1) = 80m x (1/3) = 26.67m Therefore, the change in apparent depth is 26.67 meters, which is closest to the option labeled "15m".