Lesson Notes By Weeks and Term v4 - SHS 3
ATOMIC PHYSICS
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ATOMIC PHYSICS
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Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 19
Grade code: 3.4.1.LI.3
Strand code: 4
Sub-strand code: 1
Content standard code: 3.4.1.CS.1
Indicator code: 3.4.1.LI.3
Theme: ATOMIC AND NUCLEAR PHYSICS
Subtheme: ATOMIC PHYSICS
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Welcome, my dear students. Today, we delve into a fascinating and powerful part of the electromagnetic spectrum: X-rays. You have likely heard of X-rays from visits to the hospital or seen them used at Kotoka International Airport for security scans. They are invisible rays that can pass through soft tissues but are stopped by denser materials like bone and metal. Understanding the physics behind X-rays allows us to harness their power for medicine, industry, and security. This lesson focuses on the fundamental calculations that govern their energy, frequency, and wavelength, linking back to our previous knowledge of photons and waves.
A. What are X-rays? X-rays are high-energy, high-frequency electromagnetic waves. They fall between ultraviolet (UV) rays and gamma rays on the electromagnetic spectrum. Because of their high energy, they have significant penetrating power. B. How are X-rays Produced? The most common method for producing X-rays is in an X-ray tube. Here's the simple process: A filament (cathode) is heated, causing it to release electrons through thermionic emission. A very high potential difference (voltage), V, is applied between the cathode and a metal target (anode). This high voltage accelerates the free electrons to very high speeds. These high-speed electrons smash into the metal target. Upon impact, their kinetic energy is rapidly converted into other forms, primarily heat and X-ray photons.
The key principle we will use for our calculations is the conservation of energy. The maximum possible energy of a single X-ray photon occurs when all the kinetic energy of one incoming electron is converted into the energy of that single photon. C. The Fundamental Equations
Let's gather the tools we need. These are equations you have met before, but now we will apply them specifically to X-rays.
Constants you must know: Charge of an electron, `e = 1.60 x 10⁻¹⁹ C` Planck's constant, `h = 6.63 x 10⁻³⁴ Js` Speed of light in vacuum, `c = 3.0 x 10⁸ m/s`