In Struggle: SNCC and the Black Awakening of the 1960s. Cambridge: Harvard University Press, 1995. Collier-Thomas, Bettye, and V. P. Franklin, eds. Sisters in the Struggle: African American Women in the Civil Rights-Black Power Movement. New York: New York University Press, 2001. Dudziak, Mary. Cold War Civil Rights: Race and the Image of American Democracy. Princeton: Princeton University Press, 2002. Gilmore, Glenda.
No, an X-ray is not a mechanical wave. An X-ray is an electromagnetic wave. However, in polar molecules, an X-ray can cause the molecule to vibrate rapidly, just like a microwave oven can.
(A picometer is one-trillionth of a meter.) They occupy the same region of the EM spectrum as hard X-rays. The only difference between them is their source: X-rays are produced by accelerating electrons, whereas gamma-rays are produced by atomic nuclei. This diagram shows the entire spectrum of electromagnetic waves.