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CBSE SOLUTION SCIENCE SOUND 9TH 163,165,167,168,169,170

Question: 1 – Explain how sound is produced by your school bell.
Answer:- School bell starts vibrating when heated which creates
compression and rarefaction in air and then sound startes to produce.
Question: 2 – Why are sound waves called mechanical waves?
Answer: Because sound waves do some mechanical work while making
disturbance in medium, hence It is called mechanical wave.
Question: 3 -Suppose you and your friend are on the moon. Will
you be able to hear any sound produced by your friend?
Answer: We know that  sound waves require medium to propagate and there is
no medium present on the moon. So, I will not able to hear the sound of
my friend on the moon.
Question: 1 – Question: 1 – Which wave property determines (a) loudness,(b) pitch?
Answer: (a) Amplitude of sound waves determines loudness. Louder
sound has greater amplitude and vice versa.
(b) Frequency of the sound waves determined pitch of the sound.
Question: 2 – Guess which sound has a higher pitch: guitar or car horn?
Answer: Sound of the car horn has higher pitch.
Question: 3 – What are wavelength, frequency, time period and
amplitude of a sound wave?
Answer: Wavelength: Wavelength is the distance between two
consecutive compressions or rarefaction of wave.
Frequency: The number of sound wave produced in one second is called
Time period: Time period is the time taken to produce one wave of
Amplitude: Amplitude is the maximum displacement along the mean
position of the particles of medium.
Question: 4 – How are the wavelength and frequency of a sound wave
related to its speed?
Answer: The relation between frequency and wavelenth
Velocity (v)=Wavelength(λ)X Frequency (ν), v = λX ν
This means the speed is equal to the product of wavelength and
frequency of the sound wave.
This equation is also called the ‘wave equation’ and applicable to all
types of wave.