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:
Answer:
It's the duration between successive new moons. Also called a lunation or synodic month, it has a mean period of 29.53059 days (29 days 12 hours and 44 minutes).
Answer:
low, low
Explanation:
Longer wavelengths will have lower frequencies, and shorter wavelengths will have higher frequencies.
Large amplitude waves contain more energy. The other is frequency, which is the number of waves that pass by each second. If more waves( or more wiggly lines) pass by, more energy is transferred each second
Answer:
4 m/s
Explanation:
m1 = m2 = m
u1 = 20 m/s, u2 = - 12 m/s
Let the speed of composite body is v after the collision.
Use the conservation of momentum
Momentum before collision = momentum after collision
m1 x u1 + m2 x u2 = (m1 + m2) x v
m x 20 - m x 12 = (m + m) x v
20 - 12 = 2 v
8 = 2 v
v = 4 m/s
Thus, the speed of teh composite body is 4 m/s.
Answer:
Option b. Effective nuclear charge increases as we move to the right across a row in the periodic table
Explanation:
The <em>effective nuclear charge </em>is a measure of how strong the protons in the nucleus of an atom attract the outermost electrons of such atom.
The <em>effective nuclear charge</em> is the net positive charge experienced by valence electrons and is calculated (as an approximation) by the equation: Zeff = Z – S, where Z is the atomic number and S is the number of shielding electrons.
The shielding electrons are those electrons in between the interesting electrons and the nucleus of the atom.
Since the shielding electrons are closer to the nucleus, they repel the outermost electrons and so cancel some of the attraction exerted by the positive charge of the nucleus, meaning that the outermost electrons feel less the efect of attraction of the protons. That is why in the equation of Zeff, the shielding electrons (S) subtract the total from the atomic number Z.
The <em>effective nuclear charge</em>, then, is responsible for some properties and trends in the periodic table. Here, you can see how this explains the trend of the atomic radius (size of the atom) accross a row in the periodic table.
- As the<em> effective nuclear charge</em> is larger, in a same row of the periodic table, the shielding effect is lower, the outermost electrons are more strongly attracted by the nucleus, and the size of the atoms decrease. That is why as we move to the right in the periodic table, the size of the atoms decrease.
