Which statement is true about the part of the electromagnetic spectrum that is divided into seven ranges of wavelengths?

a. it is one of three parts visible to the human eye.
b. it is the only part visible to the human eye.
c. it is one of two parts visible to the human eye.
d. it cannot be seen by the human eye unless it rains.

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?