Galileo, in order to measure the speed of light, performed this simple experiment: He and his assistant each took a lantern that had a shutter in front of it,
and stood on hilltops one mile apart in the night.
Galileo was to flash his lantern, and the assistant was to open the shutter of his own
lantern as soon as he saw the light from Galileo's lantern. Galileo had planned to
measure the time taken for light to travel from one hill to the other and back, and
calculate the speed of light using the formula, Speed = distance travelled / time
taken But he could not measure the speed of light using this method. What could
have been the reason for this?
A. The distance between the two hills was too much for them to see the light from
the other person's lantern.
B. Light does not travel in straight lines and so the distance travelled by it cannot
be measured.
C. The time taken for the light to travel would have been too little to have been
measured by them.
D. Light does not travel because it is present everywhere, so its 'speed' cannot be
calculated

The inside surface of a cylindrical-shaped cave of inner diameter 1.0 m is continuously covered with a very thin layer of water. the cave is very long and it is open on both ends. the water on the cave surface is at a constant temperature of 15.5 °c. the cave is constantly exposed to wind such that 15.5 °c air flows through the cave at 4.5 m/s. the kinematic viscosity of the air is 14.66 x 10-6 m2/s and the molecular diffusion coefficient of water vapor in the air is 0.239 x 10-4 m2/s. because the cave diameter is so large, the flow of wind down the length of the cave, in the x direction, can be treated like it is external flow and the cave surface can be approximated as flat where appropriate. calculate the x value, in a) the transition to turbulent flow occurs at rex meters, where the air flow transitions from laminar to turbulent along the inside surface of the cave b) calculate the x value, in meters, where the bulk steady state concentration of water vapor in the air flowing in the cave is 10% of the saturation concentration. assume the air at the surface of the water layer is 100% saturated with water vapor. assume the wind entering the cave contained no moisture before it entered the cave. take into account the transition from laminar to turbulent flow when solving part b