Question

how long we it take for a sound wave of 20cm wavelength and 1.2kHz frequency of, to travel a distance of 1.2km?

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Answer 1

Explanation:

Given :

Wave length of the sound is :

= 20cm or, 0.20m [∵ 1m = 100cm ]

Frequency of the sound is :

= 1.2kHz or, 1200

∴ Speed of the sound wave :

${ \underline{ \boxed{ { \odot \mid {\boldsymbol{ v = \lambda \times f }}}}}}$

Where,

• $\boldsymbol{v}$ denotes the speed.
• $\boldsymbol{f}$(frequency) = 12000Hz
• $\boldsymbol{\lambda}$(wavelength) = 0.20m

On substituting the given values :

$\longrightarrow\boldsymbol{v} = 0.20 \times 12,000$

$\longrightarrow\boldsymbol{v} = \dfrac{20}{100} \times 12,000$

$\longrightarrow\boldsymbol{v} = 20 \times 120$

$\longrightarrow\boldsymbol{v} = 2400m/s$

We know that,

$\bigstar \sf Time = \dfrac{distance}{speed}$

We have,

• distance = 1.2km or, 1200m
• Speed = 2400m/s

So,

$\sf \longrightarrow Time = \dfrac{1200}{2400}$

$\sf \longrightarrow Time = \dfrac{1}{2}$

$\sf \longrightarrow Time = 0.5s$

$\sf \therefore It \: will \: take \: \blue{ 0.5s} \: for \: the \: sound \: wave \: of \: 20cm \: with \: frequency \: of \: 1.2kHz$

Answer 2

Answer:

Given :

Wave length of the sound is :

= 20cm or, 0.20m [∵ 1m = 100cm ]

Frequency of the sound is :

= 1.2kHz or, 1200

∴ Speed of the sound wave :

{ \underline{ \boxed{ { \odot \mid {\boldsymbol{ v = \lambda \times f }}}}}}

⊙∣v=λ×f

Where,

\boldsymbol{v}v denotes the speed.

\boldsymbol{f}f (frequency) = 12000Hz

\boldsymbol{\lambda}λ (wavelength) = 0.20m

On substituting the given values :

\longrightarrow\boldsymbol{v} = 0.20 \times 12,000⟶v=0.20×12,000

\longrightarrow\boldsymbol{v} = \dfrac{20}{100} \times 12,000⟶v=

100

20

×12,000

\longrightarrow\boldsymbol{v} = 20 \times 120⟶v=20×120

\longrightarrow\boldsymbol{v} = 2400m/s⟶v=2400m/s

We know that,

\bigstar \sf Time = \dfrac{distance}{speed}★Time=

speed

distance

We have,

distance = 1.2km or, 1200m

Speed = 2400m/s

So,

\sf \longrightarrow Time = \dfrac{1200}{2400}⟶Time=

2400

1200

\sf \longrightarrow Time = \dfrac{1}{2}⟶Time=

2

1

\sf \longrightarrow Time = 0.5s⟶Time=0.5s

\sf \therefore It \: will \: take \: \blue{ 0.5s} \: for \: the \: sound \: wave \: of \: 20cm \: with \: frequency \: of \: 1.2kHz∴Itwilltake0.5sforthesoundwaveof20cmwithfrequencyof1.2kHz