The velocity of electron ejected from platinum surface is 6.54×10xm/s when radiation of 200 nm falls on it. Work function of platinum is 5eV.1eV=1.6×10−19J. The value of x is__

Using Einstein's photoelectric equation:         Ei=KE+ϕKE=Ei−ϕ1/2mV2=hv−hv0hv=1/2mV2+hvoEi: energy of incident radiation; KE: kinetic energy of electron, and ϕ: work function of metal         Ei=hcλ=6.63×10−34×3×108200×10−9=9.945×10−19J ϕ=5eV=5×1.6×10−19J=8.0×10−19J⇒ Ek=Ei−ϕ=9.945×10−19−8.0×10−19 Now  Ek=1/2mv2⇒v=2Ekm⇒ v=21.195×10−199.1×10−31=6.54×105m/s