Which particle among the following will have the smallest de-broglie wavlength, retriceuming that they have the same velocity
a) a positron c)an a-particle
b) a photon d) a neutron

Question

Which particle among the following will have the smallest  de-broglie wavlength, retriceuming that they have the same velocity
a) a positron           c)an a-particle
b) a photon             d) a neutron

dominusscholae · Answer

De Broglie Wavelength = 
$$h/p, $$ h = Planck's constant, p = momentum = mass*velocity. Assuming the velocity is the same, the smallest wavelengths will be for the particles with the GREATEST MASS. Thus, which one here has the greatest mass?

anonymous · Answer

i too dont know

dominusscholae · Answer

Hint: An alpha particle has two protons and two neutrons. Photon is massless. Positron is same mass as electron. Electron's mass < Proton's mass.

anonymous · Answer

but the ans. is given a-particle.

dominusscholae · Answer

yes, since it consists of two protons and two neutrons, which is heavier than the rest.

anonymous · Answer

so a-particle has largest de-broglie wavelength among the above??

dominusscholae · Answer

Yes

anonymous · Answer

ok thanks