Ncert Exercises & Solutions

Identify the matter waves with the shortest wavelength when traveling at the same speeds :

1.	Electron	2.	Alpha particle (He²⁺)
3.	Neutron	4.	Proton

Hint: De brogile equation

From de-Broglie equation,

wavelength, λ = \frac{h}{mv}

For the same speed of different particles, i.e., electron, proton, neutron and

α

-particle,

λ \propto \frac{1}{m}

As h is constant. Greater the mass of matter waves, lesser is wavelength and vice-versa. In these matter waves, alpha

particle (He²⁺) has a higher mass, therefore, shortest wavelength.