A photon of wavelength λ is scattered from an electron, which was at rest. The wavelength shift Δ λ is three times of λ and the angle of scattering θ…

A photon of wavelength $\displaystyle \lambda$ is scattered from an electron, which was at rest. The wavelength shift $\displaystyle \Delta \lambda$ is three times of $\displaystyle \lambda$ and the angle of scattering $\displaystyle \theta$ is $\displaystyle 60^{\circ}$. The angle at which the electron recoiled is $\displaystyle \phi$. The value of $\displaystyle \tan \phi$ is : (electron speed is much smaller than the speed of light)