Figure P8.21 depicts a beaker containing a block of glass on the bottom and water over it.

Question:

Figure P8.21 depicts a beaker containing a block of glass on the bottom and water over it. The glass block contains a small air bubble at an unknown depth below the water surface. When viewed from above at an angle of 60_, the air bubble appears at a depth of 6.81 cm. What is the true depth of the air bubble?