An X-Ray tube is operated at 150Kv at 10mA . if only 1% of electric power supplied is converted into X-Ray ,the rate at which the target is hitted is (in Cal/s
I dont understand exactly is done in the experiment
OK. What happens is that high energy electrons are fired at the metal target and they collide with electrons in the metal atoms and eject them. So you are left with metal ions with a hole where their electron used to be. OK so far?
Any electron can be ejected, but what is of interest here is when an electron is ejected from the 1s orbital. For historical reasons the 1s is known as a the K shell, so you'll often see these described a K electrons.
When this happens an electron drops down from the 2s orbital into the 1s orbital, and the energy difference is emitted as a photon.
So the end result is that we get a photon emitted with an energy equal to the 2s -> 1s transition.
An X-Ray tube is operated at 150Kv at 10mA . if only 1% of electric power supplied is converted into X-Ray ,the rate at which the target is hitted is (in Cal/s
We are told the tube is operated at 10mA, and I assume this means the beam current is 10mA. That means 0.01 coulombs per second hit the metal. Divide 0.01 coulombs by the electron charge and you have the number of electrons per second hitting the target.
I make this $6.24 \times 10^{16}$ electrons per second.
The other 99% either go straight through the metal target without hitting anything, or they lose their energy in mutliple low energy collisions that don't emit an X-ray.
A current is the flow of electrons. Normally we have electrons flowing in a wire, but if you have electrons travelling through a vacuum then that is a current as well.
In an X-ray tube electrons are emitted at one end then accelerated towards the metal target, where their collisions with the metal emit X-rays. So there is a current flowing along the tube due to the electrons travelling from the end of the tube along the tube to the metal.
The electrons are emitted at the cathode and they travel through the vacuum inside the X-ray tube and hit the metal target (the tungsten target in this case).
@Jasmine no, the electrons don't disappear if they collide and cause a photon to be emitted. They just lose energy in the collision and then carry on round the circuit.
Yes, so the electron loses its kinetic energy and stops. But the 150kV battery is driving the electrons round the circuit, so that electron carries on round the circuit.
Electrons carry an electric charge (of $-e$) so if they just disappeared charge wouldn't be conserved. Photons have no charge so it doesn't cause any problems with charge conservation if they appear and disappear.
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