The faster a sound wave travels, the more distance it will cover in the same period of time. If a sound wave were observed to travel a distance of 700 meters in 2 seconds, then the speed of the wave would be 350 m/s. A slower wave would cover less distance-perhaps 660 meters-in the same time period of 2 seconds and thus have a speed of 330 m/s.
Melanoma Definition. Melanoma is a form of skin cancer that arises from melanocytes-the cells that produce pigment. Melanoma may begin in association with a mole. Melanocytes produce a pigment called melanin that gives the skin its colour and protects it from sun damage.
Malignant melanoma is a neoplasm of melanocytes or of the cells that develop from melanocytes. (See the images below.) Although melanoma was once considered an uncommon disease, the annual incidence has increased dramatically over the past few decades, as have deaths from melanoma. (See Etiology and Epidemiology.)