INTRODUCTION 2 STREET BEATS Can you hear it It's your favorite band playing at a concert The music gets louder and louder the closer you get to the stage In the crowd everyone's dancing You can all feel the beat The low bass is pounding in your chest The stage lights switch from red to yellow and blue A spotlight follows the lead singer Flashing lights highlight You can feel a song's low bass notes in your body but not the higher notes That is because sound travels in waves The low notes have longer waves that move more slowly So you can feel them as they travel through body your
Sound and light waves make a concert loud and exciting the beat Their light travels in waves You don't feel the light waves but they help you see everything around you Ever wonder why low sounds make your body vibrate Or why a leaf is green Or even how bats can fly in the dark Scientists ask these kinds of questions as they study the world and wonder how it works They test their theories and come up with answers based on their evidence This is known as scientific inquiry What questions do you have about sound and light 5
CHAPTER 1 HOW DOES LIGHT TRAVEL ave you ever done the wave at a football game One section of the crowd stands up waving their arms They sit down and then the next section does it The movement travels from one part of the stadium to the next The crowd's wave starts at a source That's where the energy is most Fans at a sports stadium demonstrate intense From there the the basic properties of sound and light waves energy spreads Sound and light travel in a way that is similar to the crowd's wave at a football game They are forms of energy that move in waves from a source Their energy spreads out from a source in directions all
7 Although we cannot see waves in light scientists observed other waves in nature for clues about the nature of light Thomas Young's observations of the waves in water inspired him to hypothesize about how light waves travel TRANSVERSE WAVES Have you seen a duck rising and falling as it floats on the water The duck moves with the water's waves as they travel to the shore This type of wave is known as a transverse wave a wave that travels in a perpendicular direction along its path The high point of this kind of wave the part where the duck bobs up in the water is called the crest The low point where the duck dips down is the trough In the early nineteenth century British doctor Thomas Young used his observations of transverse waves in water to help him determine how light traveled Since the late seventeenth century there had been two theories about light one insisted light was made of waves and the other said that light was made particles of
