The document describes calculating the energy of photons and kinetic energy of electrons with a wavelength of 0.281 nm. It states that the energy of photons is 4.4127 eV and the kinetic energy of electrons is 19.05 eV.

1. 1
In designing an
experiment, you want a
beam of photons and a
beam of electrons with
the same wavelength of
0.281 nm, equal to the
separation of the Na and
Cl ions in a crystal of
NaCl. Find the energy of
the photons and the
kinetic energy of the
electrons.
HELPING TOOLS
No.1

2. 2
No.2
No.3

3. 3
Solution
15
9
8
15
9
2
3
3
We know that
4.136 10 .
0.281 10
2.998 10
4.136 10 .
0.281 10
44.127 10 4412.7
4.4127 10
Note: Both photon & electron have
equal momentum, i.e. 4.4127X10
E hf h X eV s
p
c c X m
m
X
X eV s s
X
X m c
eV eV
X
c c
eV
X
c
eV
c

−
−
−
−
= = = =
=
= =
=
3
3
Now, energy of photon is
4.4127 10
4.4127 10
eV
E pc X Xc
c
X eV
= =
=

4. 4
2
2
2 2 2
2 2
3 2
6 2
Now, let us calculate the
KE of electron as under:
1
K &
2 2
( )
2 2
(4.4127 10 )
2 511000
19.47 10 ( )
1022000
19.05
p
mv p mv K
m
p c pc
K X
m c mc
X eV
X eV
X eV
eV
eV
= =  =
 = =
=
=
=