The sound of a loud warning siren travels through air and reaches the surface of a lake. the sound is then transmitted through the water at a speed about four times faster than through air. how will the frequency and wavelength in water compare to these same measurements in air?

The wavelength will increase by a factor of four, but the frequency will not change.   

Because its reliable.   there is no pollution  the chances of a radiation leak is low

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.