[ 461 ] Physical Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Refer to the following passage to answer the next nine questions. In the late seventeenth century, Isaac Newton explained light as consisting of particles. But, in the early twentieth century, physicists began explaining light, not as a particle, but rather as a wave. A wave is a periodic oscillation. The shape of a wave starts from a zero level and increases to the highest point or crest. Then, it decreases past zero to its lowest level or trough. From the trough, it rises again to zero. This wave pattern repeats itself over time. The wave has three properties that describe it: amplitude, wavelength, and frequency. Amplitude (A) is the distance from the zero point to the crest of the wave and has the SI unit of meters (m). Wavelength (λ) is the distance from the peak of one wave to the peak of the next wave or the trough of one wave to the trough of the next wave; λ has the SI unit of meters (m). The frequency (ν) is the number of wave cycles per unit of time; the SI unit of frequency is the hertz (Hz). The speed of a wave is the product of the wavelength and the frequency. In the case of a light wave, the speed of light (c) is a constant (3 × 10 8 m/s) and is described by this formula: c = λν. The wavelengths of light vary from extremely short gamma rays (λ < 10 –12 m) to very long radio waves (λ > 1 m). According to this passage, what is a wave? A. the distance from one peak to the next B. the highest point C. a periodic oscillation D. the distance from the zero point to the highest point According to this passage, what is a crest? A. the distance from one peak to the next B. the highest point C. a periodic oscillation D. the distance from the zero point to the highest point