Given the one-dimensional wave equation d2e/dz2=k d2e/dt2and using the change of variables r= t+ k1/2z and s= t- k1/2z solve the equation.

probably not if net force is zero

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray