Question

The wavelength of two waves are 50 and 51 cm respectively. If the temperature of the room is 20°C then what will be the number of beats produced per second by these waves, when the speed of sound at 0°C is 332 m/s?

विकल्प

• 24

• 14

• 10 

• none of these

Answer 1

14

Explanation:

λ₁ = 50 cm     λ₂ = 51 cm.

v ∝ `sqrt"T"` ⇒ `"v"_1/"v"_2=sqrt("T"_2/"T"_1)=sqrt((273+20)/273)`

⇒ v₂ = 319.23

v₁ = `"v"_2/lambda_1=319.23/0.50` = 640 Hz.

v₂ = `"v"_2/lambda_2=319.23/(51xx10^-2)` 

=  625.94 = 626 Hz.

No. of beats = v₂ - v₁ = 14 Hz.