Question

when a wave travels from one medium to another the wavelength change but not the frequency the wavelength of sound disturbance 30cm in air and of wave velocity is 340m/s what will be the wavelength of this disturbance in helium and water? the speed of sound in helium is 970m/s and 1450m/s .in water

Answer 1

we know frequency = velocity/wavelength
if frequency is constant then,velocity in air / wavelength in air
                                              =velocity in helium / wavelength in helium 
                                              =velocity in water / wavelength in water
wavelength in air = 30 cm = 0.3 m
velocity in air / wavelength in air = velocity in helium / wavelength in helium 
340/0.30 = 970 / wavelength in helium 
wavelength in helium = 0.855 m = 85.5 cm
velocity in air / wavelength in air = velocity in water / wavelength in water
340 / 0.30 = 1450 / wavelength in water
wavelength in water = 1.279 m = 127.9 cm 

Answer 2

Answer:

velocity /wave length

velocity in air /wavelength in air

340/0.30=970/wavelength in helium

0.8555m=85.5m

340/0.30=1450

1.279m=127.9m