NGSS MS-PS4-1, 4-2, 4-3 Study Guide Waves Can be edited for younger or older learners. Use as a study guide, on-going guide for research, or assessment. Vocabulary- Write the definition for the following words. Amplitude Wavelength Crest Trough Medium Reflection Transmission Wave Propagation Absorption Light Wave Mechanical Wave Sound Wave Water Wave Analog Signal Digital Signal Hertz Electromagnetic wave Longitudinal Wave Rarefaction Compression Understanding Concepts 1) Describe the differen