Chapter 11: Sound Short Questions | science Class 9 CBSE

ByteNotes

Chapter 11: Sound Short Questions | science Class 9 CBSE | ByteNotes.in

Short Answer

Direct answer format

Short Answer

Question 1

Quick Recall

Q1. What causes sound?

Sound is caused by vibrations of objects.
These vibrations create compressions and rarefactions.
Sound needs a medium to travel.

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 2

Quick Recall

Q2. Define frequency and give its SI unit.

Frequency is the number of oscillations per second.
It determines pitch of the sound.
SI unit: hertz (Hz).

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 3

Quick Recall

Q3. Define wavelength.

Wavelength is the distance between two consecutive compressions or rarefactions.
Denoted by λ (lambda).
Measured in metres (m).

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 4

Quick Recall

Q4. What is amplitude?

Amplitude is the maximum displacement of particles from their mean position.
It determines the loudness of sound.
Greater amplitude = louder sound.

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 5

Quick Recall

Q5. Write the speed of sound in air at 25°C.

Speed of sound in air at 25°C is approximately 346 m/s.
It increases with temperature.
Faster in solids than gases.

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 6

Quick Recall

Q6. Define pitch.

Pitch is the perception of frequency of sound.
Higher frequency = higher pitch.
Used to distinguish notes in music.

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 7

Quick Recall

Q7. What is echo?

Echo is a reflected sound heard after a time gap.
Occurs if reflected sound takes more than 0.1 s to reach the ear.
Requires a minimum distance of 17.2 m.

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 8

Quick Recall

Q8. State two applications of reflection of sound.

Used in stethoscope to direct sound to ears.
Megaphones and soundboards reflect and direct sound.
Used in auditorium design for sound clarity.

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 9

Quick Recall

Q9. What is ultrasound?

Sound with frequency above 20,000 Hz.
Cannot be heard by humans.
Used in medical imaging and industry.

ByteNotes

Short Answer

Direct answer format

Short Answer

Question 10

Quick Recall

Q10. Define time period.

Time taken for one complete vibration.
Denoted by T.
Measured in seconds (s).

ByteNotes

Chapter sections

Chapter 11: Sound | Short Questions

Q1. What causes sound?

Q2. Define frequency and give its SI unit.

Q3. Define wavelength.

Q4. What is amplitude?

Q5. Write the speed of sound in air at 25°C.

Q6. Define pitch.

Q7. What is echo?

Q8. State two applications of reflection of sound.

Q9. What is ultrasound?

Q10. Define time period.