{"id":2527,"date":"2026-05-28T17:12:42","date_gmt":"2026-05-28T11:42:42","guid":{"rendered":"https:\/\/mymockmate.com\/notes\/?p=2527"},"modified":"2026-05-28T17:12:46","modified_gmt":"2026-05-28T11:42:46","slug":"ncert-class-9-science-sound-waves-characteristics-and-applications-solutions","status":"publish","type":"post","link":"https:\/\/mymockmate.com\/notes\/ncert-class-9-science-sound-waves-characteristics-and-applications-solutions\/","title":{"rendered":"NCERT Class 9 Science Sound Waves Characteristics and Applications Solutions"},"content":{"rendered":"<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2527?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\" ><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\" \/><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">1<\/span><\/div>\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Short Intro<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">This chapter explains how sound is produced, propagated, reflected, and perceived by humans. Students will learn about sound waves, compressions and rarefactions, wavelength, frequency, amplitude, echo, reverberation, ultrasonic waves, sonar, and practical applications of sound in daily life.<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Quick Information Box<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Topic<\/th><th>Details<\/th><\/tr><\/thead><tbody><tr><td>Chapter Name<\/td><td>Sound Waves: Characteristics and Applications<\/td><\/tr><tr><td>Class<\/td><td>Grade 9<\/td><\/tr><tr><td>Subject<\/td><td>Science<\/td><\/tr><tr><td>Wave Type<\/td><td>Longitudinal Mechanical Wave<\/td><\/tr><tr><td>Audible Range<\/td><td>20 Hz to 20 kHz<\/td><\/tr><tr><td>Speed of Sound in Air<\/td><td>Approximately 340 m\/s<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h1 class=\"wp-block-heading\">Concepts Used (Topics Covered)<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Production of Sound<\/li>\n\n\n\n<li>Propagation of Sound<\/li>\n\n\n\n<li>Longitudinal Waves<\/li>\n\n\n\n<li>Compression and Rarefaction<\/li>\n\n\n\n<li>Mechanical Waves<\/li>\n\n\n\n<li>Wavelength, Frequency and Time Period<\/li>\n\n\n\n<li>Amplitude and Loudness<\/li>\n\n\n\n<li>Speed of Sound<\/li>\n\n\n\n<li>Echo and Reverberation<\/li>\n\n\n\n<li>Reflection of Sound<\/li>\n\n\n\n<li>Ultrasonic and Infrasonic Waves<\/li>\n\n\n\n<li>Sonar and Echolocation<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Important Formulas<\/h1>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Frequency<br>\u03bd = Number of Oscillations \/ Time<\/li>\n\n\n\n<li>Time Period<br>T = 1 \/ \u03bd<\/li>\n\n\n\n<li>Speed of Sound<br>v = \u03bd\u03bb<\/li>\n\n\n\n<li>Distance Formula<br>Distance = Speed \u00d7 Time<\/li>\n\n\n\n<li>Echo Distance<br>Distance = (v \u00d7 t)\/2<\/li>\n<\/ol>\n\n\n\n<h1 class=\"wp-block-heading\">Questions &amp; Step-by-step Solutions with Explanation<\/h1>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q1. Sound as Mechanical Wave<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Question:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Which observation best supports that sound is a mechanical wave?<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Options:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">(i) Sound shows reflection<br>(ii) Sound needs a medium to propagate<br>(iii) Sound has frequency<br>(iv) Sound carries energy<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Mechanical waves require a material medium for propagation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">(ii) Sound needs a medium to propagate<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q2. Frequency and Oscillations<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Question:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">If 20 compressions pass a point in 4 seconds, find frequency.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Formula:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Frequency = Oscillations \/ Time<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Calculation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = 20 \/ 4<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = 5 Hz<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">5 Hz<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q3. Echo or Reverberation<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Question:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Reflected sound reaches ear after 0.05 s. Is it echo or reverberation?<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Echo requires minimum 0.1 s gap.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Since time gap is less than 0.1 s, reflected sound overlaps with original sound.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">It is reverberation.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q4. Compare Sound Waves<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Greater wavelength \u2192 wave with larger crest-to-crest distance<\/li>\n\n\n\n<li>Smaller amplitude \u2192 wave with smaller height<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Students should identify directly from graph.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q5. Frequency Identification<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Higher frequency means more oscillations in same distance.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A \u2192 Highest frequency<\/li>\n\n\n\n<li>C \u2192 Lowest frequency<\/li>\n\n\n\n<li>B \u2192 Intermediate frequency<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q6. Draw Sound Wave<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Wave should have:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Amplitude = 3 units<\/li>\n\n\n\n<li>Wavelength = 4 cm<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Draw proper crest and trough distances.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q7. Spacecraft Explosion Error<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Two errors:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Sound cannot travel in vacuum of space.<\/li>\n\n\n\n<li>Sound and light cannot arrive together because sound is much slower.<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q8. Time Period Calculation<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Given:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Wavelength = 3.44 m<br>Speed = 344 m\/s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Formula:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">v = \u03bd\u03bb<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = v\/\u03bb<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = 344 \/ 3.44<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = 100 Hz<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Time Period:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">T = 1\/\u03bd<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">T = 1\/100<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">T = 0.01 s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">0.01 second<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q9. Sonar Problem<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Given:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Time = 5 s<br>Speed = 1525 m\/s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Formula:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Distance = (v \u00d7 t)\/2<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Calculation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Distance = (1525 \u00d7 5)\/2<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 3812.5 m<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Depth of ocean = 3812.5 m<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q10. Ultrasonic Parking Sensor<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Given:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Distance = 1.2 m<br>Speed = 345 m\/s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Total Distance:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 2 \u00d7 1.2<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 2.4 m<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Time:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">t = Distance \/ Speed<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 2.4 \/ 345<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u2248 0.00696 s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">0.007 second approximately<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q11. Thunder Sound Delay<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Given:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Distance = 1720 m<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">At 22\u00b0C:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Time = 1720 \/ 344<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 5 s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">At 0\u00b0C:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Time = 1720 \/ 331<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u2248 5.2 s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Extra Time:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 5.2 \u2212 5<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 0.2 s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Thunder takes approximately 0.2 s extra.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q12. Frequency from Graph<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Given:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Wave speed = 340 m\/s<br>Wavelength from graph = 8 cm<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Convert:<br>8 cm = 0.08 m<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Formula:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = v\/\u03bb<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = 340 \/ 0.08<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 4250 Hz<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Frequency = 4250 Hz<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q13. Frequency of Waves A and B<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Given:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Speed = 345 m\/s<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Students measure wavelength directly from graph.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Formula:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u03bd = v\/\u03bb<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Use wavelength values from graph for calculation.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q14. Sound in Air and Water<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Given:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Time in air = 4.5 \u00d7 Time in water<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Since distance is same:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Speed \u221d 1\/Time<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ratio:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Speed in air : Speed in water<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 1 : 4.5<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Simplified:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">2 : 9<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">2 : 9<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q15. Assertion and Reason<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Assertion:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">We cannot hear bell ringing in evacuated jar.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Reason:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Sound requires medium to travel.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">(ii) Both A and R are true and R correctly explains A.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q16. Compression and Rarefaction Assertion<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Assertion:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Compressions and rarefactions move through medium.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Reason:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Particles continuously move forward with wave.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Particles only vibrate about mean positions.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">(iii) A is true but R is false.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q17. Energy Transfer in Sound<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Question:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">What actually reaches ear from tuning fork?<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Energy travels through sound waves.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Particles themselves do not travel to ear.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">(ii) Energy carried by sound waves<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Common Mistakes<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Confusing loudness with intensity<\/li>\n\n\n\n<li>Using wrong units for wavelength<\/li>\n\n\n\n<li>Forgetting echo distance is half distance travelled<\/li>\n\n\n\n<li>Mixing frequency and time period<\/li>\n\n\n\n<li>Assuming particles travel with sound wave<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Exam Tips<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Learn all sound formulas carefully.<\/li>\n\n\n\n<li>Practice numerical problems regularly.<\/li>\n\n\n\n<li>Remember audible range values.<\/li>\n\n\n\n<li>Draw labelled wave diagrams neatly.<\/li>\n\n\n\n<li>Always convert cm into m before calculations.<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Practice MCQs<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">1. Sound waves are:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Transverse waves<br>B. Longitudinal waves<br>C. Electromagnetic waves<br>D. Stationary waves<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Longitudinal waves<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">2. SI unit of frequency:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Joule<br>B. Newton<br>C. Hertz<br>D. Pascal<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. Hertz<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">3. Human audible range:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. 2 Hz \u2013 200 Hz<br>B. 20 Hz \u2013 20 kHz<br>C. 200 Hz \u2013 2 MHz<br>D. 100 Hz \u2013 1000 Hz<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. 20 Hz \u2013 20 kHz<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">4. Sound cannot travel through:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Air<br>B. Water<br>C. Steel<br>D. Vacuum<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">D. Vacuum<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">5. Instrument used in underwater detection:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Radar<br>B. Sonar<br>C. Microscope<br>D. Periscope<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Sonar<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">FAQ Section<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Q1. Why is sound called a mechanical wave?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Because it requires a material medium to travel.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q2. What is wavelength?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Distance between two consecutive compressions or rarefactions.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q3. What is frequency?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Number of oscillations per second.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q4. Why do we hear echo?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Due to reflection of sound from distant surfaces.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q5. What are ultrasonic waves?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Sound waves having frequency above 20 kHz.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Master Science with chapter-wise notes, detailed solutions, MCQs, quizzes, and mock tests only on <a href=\"http:\/\/www.mymockmate.com\/\">www.mymockmate.com<\/a> and boost your exam preparation today!<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2527?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\" ><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\" \/><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">1<\/span><\/div>\n    <div class=\"xs_social_share_widget xs_share_url after_content \t\tmain_content  wslu-style-1 wslu-share-box-shaped wslu-fill-colored wslu-none wslu-share-horizontal wslu-theme-font-no wslu-main_content\">\n\n\t\t\n        <ul>\n\t\t\t        <\/ul>\n    <\/div> \n","protected":false},"excerpt":{"rendered":"<p> 1 Short Intro This chapter explains how sound is produced, propagated, reflected, and perceived by humans. Students<\/p>\n","protected":false},"author":3,"featured_media":2530,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_surecart_dashboard_logo_width":"180px","_surecart_dashboard_show_logo":true,"_surecart_dashboard_navigation_orders":true,"_surecart_dashboard_navigation_invoices":true,"_surecart_dashboard_navigation_subscriptions":true,"_surecart_dashboard_navigation_downloads":true,"_surecart_dashboard_navigation_billing":true,"_surecart_dashboard_navigation_account":true,"postBodyCss":"","postBodyMargin":[],"postBodyPadding":[],"postBodyBackground":{"backgroundType":"classic","gradient":""},"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[22,4,12],"tags":[1389,1390,1388,1396,1395,1393,1392,1394,1391],"class_list":["post-2527","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cbse","category-class-9","category-science","tag-echo","tag-frequency","tag-infrasound","tag-longitudinal-waves","tag-reverberation","tag-sound-waves","tag-speed-of-sound","tag-ultrasound","tag-wavelength"],"jetpack_publicize_connections":[],"_links":{"self":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2527","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/comments?post=2527"}],"version-history":[{"count":2,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2527\/revisions"}],"predecessor-version":[{"id":2648,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2527\/revisions\/2648"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media\/2530"}],"wp:attachment":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media?parent=2527"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/categories?post=2527"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/tags?post=2527"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}