NCERT Solutions for Class 9 Science Chapter 12
NCERT Solutions for Class 9 Science Chapter 12 Sound intext questions on Page 162 or Page 163 or Page 166 or Page 167 or Page 168 or Page 169 or Page 170 or Page 172 and Exercises in English Medium free to download in PDF updated for new academic session 2020-21.Download Hindi Medium solutions of Class 9 Science Chapter 12 given on पेज 182 के उत्तर or पेज 186 के उत्तर or पेज 187 के उत्तर or पेज 188 के उत्तर or पेज 189 के उत्तर or पेज 190 के उत्तर or पेज 191 के उत्तर or पेज 193 के उत्तर and अभ्यास के प्रश्न उत्तर in PDF form. NCERT Solutions Apps 2020-21 based on latest NCERT Books 2020-2021 following new CBSE Curriculum 2020-21 are free to download in PDF form.
NCERT Solutions for Class 9 Science Chapter 12
|Subject:||Science – विज्ञान|
9th Science Chapter 12 Answers in English & Hindi Medium
CBSE NCERT Solutions for Class 9 Science Chapter 12 Sound all intext question answers and Exercises question answers are given below to free download. Visit to Discussion Forum to ask your doubts and respond to the questions asked by other users. Download Offline Apps 2020-21 based on latest NCERT Books for session 2020-2021.
9th Science Chapter 12 Answers in English Medium
- Page 162 Question – Answers
- Page 163 Question – Answers
- Page 166-A Question – Answers
- Page 166-B Question – Answers
- Page 166-C Question – Answers
- Page 167 Question – Answers
- Page 168 Question – Answers
- Page 169 Question – Answers
- Page 170 Question – Answers
- Page 172 Question – Answers
- Exercises Question – Answers
9th Science Chapter 12 Answers in Hindi Medium
9th Science Chapter 12 Answers in PDF Form
- Download Page 162 Answers
- Download Page 163 Answers
- Download Page 166-A Answers
- Download Page 166-B Answers
- Download Page 166-C Answers
- Download Page 167 Answers
- Download Page 168 Answers
- Download Page 169 Answers
- Download Page 170 Answers
- Download Page 172 Answers
- Exercise Question Answers
- Study Material for 2020-21 in English
- Study Material for 2020-21 in Hindi
Distinguish between music and noise?
1. It has a pleasant effect on the ear.
2. It consists of a series of sound impulses which follow one another regularly.
3. The frequency of musical sound is high
4. There are no sudden changes in amplitude (loudness) of the wave constituting a musical sound.
1. It has an unpleasant effect on the ear.
2. The sound impulses do not follow one another regularly.
3. The frequency of noise is low.
4. There are usually sudden changes in amplitude (loudness) of the wave forming a noise.
What is SONAR? How is it used to detect an underwater object and measure its distance?
It is an acronym which means Sound Navigation And Ranging.
Sonar is a device which measures the distance, direction and speed of objects lying under water ultrasonic waves.
The above method of finding the distance of an object is called echo-ranging as it is based on echo principle. The sonar technique is used to:
1. To locate the position of other ships or submarines. Ship to ship communication also uses ultrasonic waves. The advantage of using ultrasonic waves is that these waves cannot be heard without the aid of special instruments.
2. Determine depth of the sea , called echo depth ranging. When used for purpose , it is called fathometer as it directly fathoms the depth of the sea.
3. Locate underwater hills, valleys, icebergs, submarines and sunken ships.
Chandigarh radio station broadcast at 1200 kHz. At what metre Chandigarh station would be tuned in your transistor?
A hospital uses an ultrasonic scanner to locate tumour in a tissue. What is the wavelength of sound in a tissue in which the speed of sound is 1.7 km/s? The operating frequency of the scanner is 4.2 MHz .
Questions for Practice on 9th Science Chapter 12
An engine is approaching a hill at constant speed when it is at a distance of 0.9 km, if blows a whistle, whose echo is heard by the driver after 5 s. if the speed of sound is 340 m/s, calculate the speed of the engine.
A person standing between two vertical cliffs and 680 m away from the nearest cliff, shouted . he heard the first echo after 4 s and the second echo 3 s later, calculate (a) the speed of sound in air and (b) distance from the two cliffs.
(a) 340 m/s
(b) 1870 m
A sonar emits pulses on the surface of water which are detected after reflection from its bottom at a depth of 1534 m. if the time interval between the emission and detection of the pulse is 2 s, find the speed of sound in water.
A bat emits unit ultrasonic sound of frequency 100 kHz in air. If this sound meets a water surface, what is the wavelength of (a) the reflected sound wave (b) the transmitted sound wave. Given speed of sound in air = 340 m/s and in water = 1486 m/s.
(a)3.4 x 10-³ m
(b) 1.486 x 10-²
Important Questions on 9th Science Chapter 12
For example: A vibrating tuning fork, a bell, wires in a sitar and a guitar etc.
Number of vibrations of the source in 1 second = 100
Number of vibrations of the source in 1 minute (i.e., 60 second) =100×60 = 6000
⇒ v = λv
To reduce reverberation, the roof and walls of the auditorium are generally covered with sound-absorbent materials like compressed fibreboard, rough plaster or draperies. The seat materials are also selected on the basis of their sound absorbing properties.
तीव्रता: किसी एकांक क्षेत्रफल से एक सेकेंड में गुजरने वाली ध्वनि ऊर्जा को ध्वनि की तीव्रता कहते है।