Skip to main content
SS
Uploaded bySandeep Swamy
157 views
Chapter-10-Sound-Waves-Characteristics-and-Applications.pdf//ppt// Prepared by K Sandeep Swamy (M.Sc, B.Ed) // For ONLINE Classes (ACADEMICS,IITJEE & NEET ) Contact 9491878325 // Subscribe samyans Eduhub youtube channel
Class 9 chapter–10 Science Chapter 10: Sound Waves — Characteristics and Applications A deep dive into how sound is produced, how it travels, and the remarkable ways we use it in nature, medicine, and technology. Chapter 10 — Grade 9 Science Prepared by K Sandeep Swamy (M.Sc, B.Ed) For ONLINE Classes (ACADEMIC,IITJEE & NEET ) Contact 9491878325 Subscribe samyans Eduhub youtube channel Think It Over: Can Astronauts Hear Each Other in Space? Astronauts in Space Two astronauts on a spacewalk — can they hear each other speak or hear metal clanking? Bats in the Dark How do bats locate prey in complete darkness at night with such precision? The Big Ideas These questions reveal two central themes: how sound travels and what it can do. Section 10.1 Production of Sound Every sound you have ever heard began with something vibrating. Let's explore what that means. Sound is Produced by Vibrations Vibration: periodic to-and-fro (oscillatory) motion of an object Plucking a rubber band → it vibrates → sound is produced; when vibration stops, sound stops Sound can be produced by vibrating strings, membranes, air columns, and other objects The object producing sound is called the source of sound How Humans and Animals Produce Sound Humans produce sound by vibrating vocal cords — tightly stretched muscular flaps inside the larynx (voice box) Tongue, lips, mouth, and nasal cavity shape sound into speech or music Grasshoppers and crickets rub wings or legs together to produce sound The Tuning Fork What is it? A U-shaped steel or aluminium bar with a stem; its prongs are struck on a rubber pad to vibrate at a precise frequency. Evidence of Vibration Vibrating prongs touching water create ripples — direct, visible proof of vibration. Why Use It? Produces a nearly single-frequency sound — ideal for controlled experiments in the lab. Section 10.2 Propagation of Sound Sound doesn't just appear at your ear — it must travel through something to reach you. Sound Travels Through Solids, Liquids, and Gases Through solids: Place your ear on a desk — you can hear a friend tapping the other end clearly Through liquids: Tapping spoons underwater — sound reaches you through water Through gases: Ordinary speech travels through air to our ears every day The material through which sound travels is called the medium Sound Cannot Travel Through Vacuum Bell Jar Experiment Electric bell rings inside a jar; as air is pumped out, sound fades; when air returns, sound returns. Mechanical Wave Sound is a mechanical wave — it requires a material medium to propagate. Astronauts in Space In outer space (near vacuum), astronauts cannot hear each other directly — they use radio devices built into their suits. Section 10.3 Sound Waves How exactly does sound move through a medium? The answer lies in compressions and rarefactions. Compressions and Rarefactions Compression (C): Region where air particles are pushed closer together — higher dens
