Respuesta :

iknowThetruth

Explanation:

velocity = wavelength × frequency => v= f1 × λ => f1 = v/ λ

λ = stays the same

v = doubles

2v = f2 × λ

2v/λ = f2

now ,

f2/f1= 2vλ/ vλ = 2

f2 = 2f1

therefore frequency is doubled