A particle of mass 4 m at rest decays into two particles of mass m and 3m having non-zero velocities. The ratio of the de Broglie wavelengths of the particles 1 and 2 is:

1/2 1/4 2 1

1

According to law of conservation of linear momentum, two particles will have equal and opposite momentum. The de Broglie wavelength is given by $λ=\frac{h}{p}$   $∴\frac{λ_1}{λ_2}=1$