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NCERT Books for Class 9 Science - Sound - Free PDF Download
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FAQs on NCERT Books for Class 9 Science Chapter 12
1. What is the difference between Longitudinal Waves of Sound and Transverse Waves as discussed in chapter 12 of the Class 9 Science NCERT book?
As stated earlier, the sound travels through a medium in longitudinal waves. These waves travel through the medium by the oscillation of the medium particles in parallel to the direction of motion which triggers the adjacent particles to move back and forth their positions and the process continues. Another type of wave is called the transverse wave which passes through the medium where the particles oscillate perpendicular to the direction of wave propagation. Just like the manner in which a pebble is thrown in the water, the waves formed on the water surface are similar to transverse waves.
2. What are the characteristics of a sound wave as discussed in chapter 12 of the Class 9 Science NCERT book?
A sound wave can be described through frequency, amplitude and speed and which changes with change in density and pressure. The number of oscillations per unit time by counting compressions and rarefactions is the frequency of the sound wave and is denoted by Hertz. The loudness or softness of the sound is determined by its amplitude, i.e., the magnitude of maximum disturbance in the medium. Speed of sound is the distance travelled by a point on a wave per unit of time. Therefore, speed= wavelength x frequency.
3. What is the application of Ultrasound waves as discussed in chapter 12 of the Class 9 Science NCERT book?
Ultrasound waves have extremely high frequencies which can travel great distances despite a number of obstacles. They are mainly used in the field of medicine and industries. First, they are used to clean electronic parts which cannot be reached easily like spiral tubes. They are used to detect cracks and flaws in metal rocks and high building structures. They are also used for echocardiography as well as in ultrasound scanners to detect internal organs and abnormalities like kidney stones.
4. What is SONAR as discussed in chapter 12 of the Class 9 Science NCERT book?
SONAR, also called Sound Navigation and Ranging, is a device that uses ultrasonic waves to detect underwater objects and measure their distance, direction and speed. It consists of a transmitter and a detector and is attached to the boat or ship. Once the transmitter sends the ultrasonic waves in a particular direction, the wavelengths get reflected after hitting the sea bed or an object which is then detected by the detector. The detector then changes the ultrasonic waves into electrical waves for interpretation.
5. How do we solve the numericals given in NCERT Books Free Download for Class 9 Science Chapter 12 - Sound?
The numericals in this chapter are very important and hence have to be solved regularly. If a student does not have access to the NCERT Books, they can easily download the study materials through the official website of NCERT or follow Vedantu for specific study resources, mock/sample papers and tips and tricks so that students can download the notes and study them offline. The numericals can only be solved if the concepts are clear and the formulas are memorised. Students must practice as many numericals in the chapter as possible to score well in the exam.