Laser Diffraction - University of Al-Ameed - 2023-2024 - PDF

University of Al-Ameed College of Medicine Department of Physiology and Medical physics Laser diffraction Asst.Lact. Hawraa H.Obaid 2023-2024 Stimulated Emission Emitted photon Incident photon Excited electron Incident photon Unexcited electron Before emission After emission Purpose: To m...

University of Al-Ameed College of Medicine Department of Physiology and Medical physics Laser diffraction Asst.Lact. Hawraa H.Obaid 2023-2024 Stimulated Emission Emitted photon Incident photon Excited electron Incident photon Unexcited electron Before emission After emission Purpose: To measurement of the wavelength of monochromatic light using the laser • Apparatus: • 1- Helium neon (He-Ne) laser. • 2- Slit. • 3- Ruler. • 4- Screen. A laser is a unique light source that emits a narrow beam of light of a single wavelength (monochromatic light). In which each wave is in phase of a single wavelength with the order near it (coherent light).A laser (which stands for light amplification by the stimulated emission of radiation) normally consists of a long narrow tube with a fully reflective mirror at one end and a partially reflective mirror at the other Show Helium- neon (He-Ne) laser. Laser light is highly directional, monochromatic and very bright. Depending on the material used to produce the laser action, the resulting beam may either be pulsed (as in the solid-state ruby laser) or continuous (as in the helium-neon gas laser). When parallel a very small object (i.e. sharp edge, slit, wire, etc.) obstructs waves of light, the waves spread around the edges of the obstruction and interfere, resulting in a pattern of dark and light fringes, and this is called the diffraction. 1. Many wavelengths 1. Monochromatic 2. Multidirectional 2. Directional 3. Incoherent 3. Coherent 9 Xm(cm) L(cm) 30 40 50 60 70 L: the distance between screen and slit. 𝑋𝑚 : Central frill . Draw the relationship between (𝑋𝑚 (cm) ) on the vertical axis and (L (cm))on the horizontal axis, then find the slope. Xm(cm) slope=? L(cm) Find (λ) from the relationship (m+1/2)λ=sin𝜃𝑑 , where (d=0.00002cm) the width of slit m=1 where, m the order of diffraction. If the wavelength of laser carbon dioxide =0.00106 cm, m=1 ,d=190 cm Find sinθ? (m+1/2)λ=sin𝜃𝑑 3/2(0.00106cm=190*sin𝜃 sin𝜃=1.5*0.00106/190 13 Classification of laser 1. Optically Pumped Solid-State Lasers I. Ruby Laser II. Nd: YAG Lasers. III. Nd: Glass Lasers 2- Liquid (Dye) Lasers 3- Gas Lasers 4- Semiconductor Lasers 5- X-ray Lasers Types of medical lasers, according the intensity of emission  has a strong emission medium emission weak emission