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I WELCOME YOU ALL TO HAVE A CUP OF PHYSICS WITH SMILE.

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Presentation on theme: "I WELCOME YOU ALL TO HAVE A CUP OF PHYSICS WITH SMILE."— Presentation transcript:

1 I WELCOME YOU ALL TO HAVE A CUP OF PHYSICS WITH SMILE

2 Discovery The discovery of X-rays was by a German physicist called Wilhelm Roentgen. In 1895 Roentgen discovered X-rays almost by accident. Whilst doing some experiments in which he passed an electric current through Crook's tubes (special tubes containing a cathode and electrode from which the air has been removed), Roentgen noticed that photographic plates nearby began to grow fogged. To discover why this occurred he placed black paper on the tube and then switched on the current. Nearby a screen coated with barium began to glow. This caused Roentgen to believe that unknown rays produced inside the tube were passing through the paper to make this fluorescent substance give out light. These he named X-rays since x is a scientific number for anything that is unknown.

3 What are X-rays? X-rays are electromagnetic waves like radio and light waves. These all travel at the speed of light, which is 300 000km per second. The wavelength of an X-ray however is one hundredth that of the light rays that you can see, at around 10¯¹ºm. This means that they have a lot more energy. X-ray fluorescence is the emission of X- rays from excited atoms produced by the impact of high-energy electrons, other particles or a primary beam of other X-rays. Atoms of all the elements emit a characteristic X-ray spectrum when they are bombarded with electrons.

4 The main use of X-rays is in medicine. A common application is in the form of X-ray machines, which take photos of a patient’s body. If an arm or leg were broken for example, then this limb would be put in front of the X-ray with a piece of photographic film behind. The X –ray is turned on briefly and goes through to the film. The rays go through the skin and flesh easily, showing up as dark areas on the film, but with more difficulty through bone. They are slowed down and so these areas are much lighter. X-rays can also be used to kill cancer cells, but also kill healthy cells, so must be used with much care. USES OF X-RAYS

5 Properties of x-rays X-rays were discovered in 1895 by the German physicist Wilhelm Conrad Röntgen - in some languages x-rays are called Röntgen-rays - and x- ray diffraction was discovered in 1912. The X-rays used in diffraction experiments all have a wavelength of 0.5-2.5 Å. The intensity of a beam of x-rays is the rate of transport of energy flow through a unit area perpendicular to the direction of propagation.

6 An x-ray machine, like that used in a doctor's or a dentist's office, is really very simple. Inside the machine is an x-ray tube. An electron gun inside the tube shoots high energy electrons at a target made of heavy atoms, such as tungsten. X-rays come out because of atomic processes induced by the energetic electrons shot at the target. Making X-rays Where do x-rays come from?

7 Beta decay can occur in two ways. As shown on the left, a neutron turns into a proton by emitting an antineutrino and a negatively charged beta particle. As shown on the right, a proton turns into a neutron by emitting a neutrino and a positively charged beta particle. Positive beta particles are called positrons and negative beta particles are called electrons.. BETA RAYS:

8 Alpha Particles An alpha particle consists of two protons and two neutrons that act as a single particle. It is identical to the nucleus of a helium atom. When an alpha particle is emitted from an unstable radioactive nucleus, the atom is transmuted into a different element. ALPHA RAYS:

9 GAMMA RAYS I don't get it. What do you mean by solid objects? Like rocks? Solid things don't travel in waves, do they? I don't get it. What do you mean by solid objects? Like rocks? Solid things don't travel in waves, do they? Gamma Rays Gamma rays, or high-energy photons, are emitted from the nucleus of an atom when it undergoes radioactive decay. The energy of the gamma ray accounts for the difference in energy between the original nucleus and the decay products. Gamma rays typically have about the same energy as a high-energy X-ray. Each radioactive isotope has a characteristic gamma-ray energy

10 MAY I FLY AWAY FROM MY PROJECT BUT I HOPE THAT MY PROJECT STAND IN YOUR MIND


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