Describe the three rays that are used to locate images formed by lenses

What type of light does this light bulb produce most (i.e. at what wavelength does the spectrum have maximum intensity)?

Water is siphoned from a large tank and discharges into the atmosphere through a 50-mm diameter tube. the end of the tube is b = 2.1 m below the tank bottom which is a = 7.4 m deep, and viscous effects are negligible. determine the maximum height h over which the water can be siphoned without cavitation occurring. atmospheric pressure is 101.4 kpa, and the water vapor pressure is 1.79 kpa (absolute)

Four friends, a, b, c, and d are standing varying distances away from a speaker which is producing sound waves.