The atomic masses of He and Ne are 4 and 20 amu respectively . The value of the de Broglie wavelength of He gas at`-73.^(@)C` is ''M'' times that of the de Broglie wavelength of Ne at `727.^(@)C.` M is

Answer

5

Explanation

The de Broglie wavelength of gas molecules is given as
`lamda=(h)/(sqrt(3mkT))` where k=Boltzmann constant
`lamda_(He)=Mlamda_(Ne)`
`(h)/(sqrt(3xx4xxkxx200))=M(h)/(sqrt(3xx20xxkxx1000))`
`M=(sqrt(3xx20xxkxx1000))/(sqrt(3xx4xxkxx200))=sqrt((20xx1000)/(4x200))=sqrt(25)=5`.