Answer: 
Explanation:
The kinetic energy of an electron 
is given by the following equation:
(1)
Where:
is the momentum of the electron
is the mass of the electron
From (1) we can find :
(2)
(3)
Now, in order to find the wavelength of the electron 
with this given kinetic energy (hence momentum), we will use the De Broglie wavelength equation:
(4)
Where:
is the Planck constant
So, we will use the value of found in (3) for equation (4):
(5)
We are told the wavelength of the photon 
is the same as the wavelength of the electron:
(6)
Therefore we will use this wavelength to find the energy of the photon 
using the following equation:
(7)
Where 
is the spped of light in vacuum
Finally:
D, you wanna know why.... cause I looked it up
Answer:
E = 3.54 x 10⁻¹⁹ J
Explanation:
The energy of the photon can be given in terms of its wavelength by the use of the following formula:
where,
E = energy = ?
h = Plank's Constant = 6.626 x 10⁻³⁴ Js
c = speed of light = 2.998 x 10⁸ m/s
λ = wavelength of light = 560.6 nm = 5.606 x 10⁻⁷ m
Therefore,
<u>E = 3.54 x 10⁻¹⁹ J</u>
In 2Cr2O7 there’s 2 items; Cr and O
