2. If the wave function is E(z,t) = 10 sin 2 ( z/(2x10-7) –1.5x1015 t), find wavelength, speed, and frequency (in SI units). 3. Derive an expression for the intensity I of a spherical wave at a distance r from its center in terms of the optical power P. What is the intensity at r =1 m for P=100 W?