Explanation:
De Broglie related the wavelength to the magnitude of the momemtum of the particle, as follows:
[tex]\lambda=\frac{h}{p}=\frac{h}{mv}[/tex]
Here h is the planck constant. The momemtum is directly proportional to the particle's mass. So, the wavelength of a particle is inversely proportional to its mass. Thus, as mass increases its wavelength decreases.