A particle of mass 3m at rest decays into two particles of masses m and 2m having non-zero velocities. The ratio of the de Broglie wavelengths of the particles (λ1λ2) is

From the law of conservation of momentum P1=P2(in opposite direction)Now the de-Broglie wavelength is given by λ=hp.So we can write the required ratio  will be equal to 1