Question

All formula of
Class 9 chapter sound( physics)

Plz

Answer 1

Velocity = Wavelenght × FrequencyVelocity = Frequency × WavelenghVelocity = (1/Time) × Wavelengh For Echo: 2 × Distance / Time = Speed of sound 

Answer 2

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.