A particle of mass M at rest decays into two particles of masses m1  and  m2having non-zero velocities. The ratio of the de-Broglie wavelengths of the particles λ1/λ2 is

By law of conservation of momentum0=m1v1→+m2v2→⇒m1v1→=−m2v2→- ve sign indicates that both the particles are moving in opposite direction. Now de-Broglie wavelengthsλ1=hm1v1and   λ2=hm2v2;∴λ1λ2=m2v2m1v1=1