Problem 5.234

An observer moves with velocity $v_{1}=\frac{1}{2} c$ along a straight line. In front of him a source of monochromatic light moves with velocity $v_{2}=\frac{3}{4} c$ in the same direction and along the same straight line. The proper frequency of light is equal to $\omega_{0} .$ Find the frequency of light registered by the observer.