Given : λ=7×10−10m Particle moves with a speed of
1
10
th. So, velocity =
1
10
×3×108=3×107ms−1 ∵λ=
h
mv
m=
h
λ.v
=
6.6×10−34J−s
7×10−10×3×107
m=0.3142×10−31kg m=0.31×10−31≈10−31kg Which is in accordance with mass of electron. Thus among the given particles, electron is the correct choice.