A star is continuously moving away from us. Then, the wavelength coming from star on the earth,

The wave function (in S.I.units) for an electromagnetic wave is given as, $\psi \left(x\text{,} t\right)={10}^3\sin \pi t\left(3\times {10}^{6}x-9\times {10}^{14}t\right)$. In the above problem, the wavelength of the wave is,