Particle $A$ of mass $m_A=\frac{m}{2}$ moving along the $x$ -axis with velocity $v_0$ collides elastically with another particle $B$ at rest having mass $m_B=\frac{m}{3}$ . If both particles move along the $x$ axis after the collision, the change $\mathrm{\Delta }\lambda$ in de-Broglie wavelength of particle $A$ , in terms of its de-Broglie wavelength $\left({\lambda }_0\right)$ before collision is: