Question

all formulas in sound chapter in physics class 9 ?

Answer 1

Formulas of sound :

(i) Echo

Speed of echo = ( 2 × distance between surface and source ) / time

(ii) V = f λ

• where V = velocity of wave ,

• f = frequency of sound wave ,

• λ = wavelength .

(iii) f = 1 / t

• where f = frequency of wave ,

• t = time period .

(iv) E = h nu

• where h = Plank's constant

• E = energy of wave .

(v) f = √T/ 2 l ( π r² d )

• f = frequency of stretched string

• l = length

• d = density

• r = radius

• T= time period .

Note that this formula is for stretched string only.

Answer 2

Given that,

Formula of sound

We need to calculate the formula of sound

(1). Echo :

Speed of echo is equal to the twice of distance between surface and source divided by time.

In mathematically term,

$v=\dfrac{2d}{t}$

Where, v = echo

d = distance between surface and source

t = time

(2). Velocity of wave :

Velocity of wave is equal to the product of frequency and wavelength.

In mathematically term,

$v=f\lambda$

Where, v = velocity of wave

f = frequency

$\lambda$ = wavelength

(3). Frequency :

Frequency is reciprocal of time.

In mathematically term,

$f=\dfrac{1}{t}$

Where, f= frequency

t = time

(4). Energy of wave :

Energy of wave is equal to the product of planck constant and frequency.

In mathematically term,

$E=h\nu$

Where, h = planck constant

$\nu$ = frequency

(5). Frequency of stretched string :

Frequency of stretched string is defined as

$f=\dfrac{1}{2L}\sqrt{\dfrac{T}{M}}$

Where, f = frequency

L = length of string

T = tension

M = mass per unit length

Hence, This is the required solution.