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1.
Force acting on a charged particle in an electric field
®
E
is given by
=
q
F
Where q = charge on the particle.
Let e be magnitude of charge on an electron;
when an electron is placed in an electric field
2.
The force acting on a charged particle in a magnetic field of intensity
B
by

= q v B sin q
Where q = angle between
and
v
= velocity of the particle.
If the magnetic field acts in a perpendicular direction, the particle undergoes a circular motion. The centripetal force is provided by the magnetic force.
mv^{2}
= q v B
r
(q = 90°, sin q = 1) Where r = radius of the particle's circular path. If the charged particle is an electron,
= e v B
and r =
mv
e B
Where e = magnitude of the charge on the electron.
3.
Electric and magnetic fields act simultaneously on an electron in a mutually perpendicular direction. The direction and magnitude of the forces due to these fields are such that they nullify each other then,
v =
Where v = velocity of electron E = intensity of electric field B = intensity of magnetic field
4.
When a charged particle is accelerated from rest through a potential difference V, the increase in kinetic energy of the particle is given by
1
mv^{2} = q V
2
5.
Energy of a photon is given by E = hv Where h = Plank's constant n = frequency of radiation
n =
C
l
\ E =
hc
Where c = velocity of electromagnetic radiation l = wavelength of radiation
6.
Einstein's photoelectric equation: hn  W_{0} =
m (v_{max})^{2}
\ hn =
m (v_{max})^{2}+w_{0}
Where hn = energy of photon of incident radiation
m(V_{max})^{2}= maximum kinetic energy of emitted photoelectrons
W_{0} = work function of the emitting metal.
7.
e V_{s} =
Where e = charge on electron V_{s} = stopping potential
m (v_{max})^{2} = maximum kinetic energy of photoelectrons
m = mass of photoelectrons V_{max} = maximum velocity of photoelectrons
8.
W_{0} = hn_{0} =
h c
Where W_{0} = work function of metal h = Plank's constant n_{0} = threshold frequency l_{0} = threshold wavelength C = velocity of light / electromagnetic radiation.
9.
hn  hn_{0} = (K.E.)_{max}
(

l_{0}
)
= (K.E.)_{max}
\ h c
l_{0}  l
l_{0}l