Osmotic pressure is calculated by the product of the concentration in molarity, the temperature, the vant Hoff factor (3 for CaCl2 and 1 for sucrose) and R, universal gas constant. At the same temperature, the osmotic pressures of both solutions are equal.
π = CRTi
For CaCl2,
π = (1)RT(3) = 3RT
For sucrose,
π = (3)RT(1) = 3RT
Possibly wet and unstable
solution:
You need to find the frequency, and they have already given you the wavelength. And since you already know the speed of light, you can use formula (2) to answer this problem. Remember to convert the nano meters to meters because the speed of light is in meters. 
