Wave pass an anchored yacht at a rate of five crests every 20 seconds. The crests are separated by a distance of 7m. Calculate 1- The frequency of the waves
2-The speed of the waves

Ahuge (essentially infinite) horizontal nonconducting sheet 10.0 cm thick has charge uniformly spread over both faces. the upper face carries +95.0 nc/m2 while the lower face carries -25.0 nc/ m2. what is the magnitude of the electric field at a point within the sheet 2.00 cm below the upper face? (ε0 = 8.85 × 10-12 c2/n · m2)