Pharmaceutical Analytical Chemistry-1 (PA-101) Lecture Notes PDF

Pharmaceutical Analytical Chemistry-1 (PA-101) Prepared by Dr. Mohamed Mahmoud El-Wekil (PhD) Lecture No. (6)  Electromagnetic spectrum (EMS)  Electromagnetic spectrum: is the range of frequencies (the spectrum) of electromagnetic radiation and their...

Pharmaceutical Analytical Chemistry-1 (PA-101) Prepared by Dr. Mohamed Mahmoud El-Wekil (PhD) Lecture No. (6)  Electromagnetic spectrum (EMS)  Electromagnetic spectrum: is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.  Electromagnetic spectrum includes ultraviolet (UV), visible (VIS), infrared (IR), gamma rays, X-rays and radio waves.  Light spreads out when it travels through narrow slit is diffraction.  The ray that will be refracted when sun rays fall on glass is red. 1  Longest wavelength is radio-waves while the shortest wavelength is gamma rays.  The color of the clear sky is blue due to phenomenon known as scattering by atmospheric particles.  White light consists of seven colors. 2  Light is electromagnetic radiation (EMR) within a certain portion of the electromagnetic spectrum.  Light has dual property (electrical and magnetic properties).  Light acts as particle and wave.  Light can travel in air and vacuum.  Speed of light is maximum in vacuum.  Prism can separate white color into original colors and acts via refraction of light. 3  Visible light is usually defined as having wavelengths in the range of 400– −7 −7 (400-700 nm), between 700 nanometers (nm), or 4.00 × 10 to 7.00 × 10 m the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).  Reflection of light is the process through which light rays falling on the surface on an object are sent back is called reflection of light. Thus, when light falls on the surface of an object it sends back the light.  Refraction of light is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media. The amount of bending depends 4 on the indices of refraction of the two media and is described quantitatively by Snell's Law. Snell's Law relates the indices of refraction n of the two media to the directions of propagation in terms of the angles to the normal.  Refractive index (n) of air =1  When light travels from air to glass, it bends to the normal plane.  Diamond is a substance with the highest refractive index value.  Refractive index is the ratio of the speed of light in a vacuum to the speed of light in the material. 5  Transmission of light rehtehw( sevaw citengamortcele fo gnivom eht si elbisivlight.lairetam a hguorht ).cte ,teloivartlu ,sevaw oidar ,  Absorption of light takes place when matter captures electromagnetic radiation, converting the energy of photons to internal energy. 6  Properties of light (waves or electromagnetic radiation):  Wave motion arises when a periodic disturbance of some kind propagated in elastic medium as air.  There are four measurable properties of wave motion such as wavelength (λ), frequency (υ, nu), amplitude and wavenumber (ύ, nu par).  Wavelength: Distance between two successive crests or troughs along the line of light (wave) propagation. Unit is nanometer (nm).  Frequency: Number of waves (cycles) per second and its unit is cycles/second or Hertz.  Wavenumber: Number of waves in cm and its unit is cm-1. 7 Wavenumber is reciprocal of wavelength in cm. ύ=1/λ Q) Calculate wavenumber of light with λ=300 nm? Answer ύ=1/λ= 1/300×10-7= 33333 cm-1 1meter= 100 cm= 1000 mm= 106 µm=109 nm= 1010 angstrom (A0) Amplitude: Maximum value reached of the variable obtained in either directions or Distance between mid-line of wave and peak of the crest or trough. Transverse wave 8  Velocity of light (C)= λ×υ= 2.8×108 m/s. λ= C/υ Energy of photons (units of light), E= hυ=hC/λ where h is Planck’s constant. As a result, E is inversely proportional to λ i.e. increase energy of light, decrease of its wavelength. Gamma rays have highest energy and so, lower λ. 9  Radio waves have lowest energy and so, higher λ. Most of EMS are used in the science of spectroscopy (interaction of EMS with matter). Interaction between matter and light in the form of electronic excitation, vibration of bonds and rotation of nuclei. 10  Figure. Types of electronic transitions n-π*> π-π*>n-σ*>σ-σ* in wavelength while vice versa in energy. 11  Color with shortest wavelength is violet and that of longest wavelength is red.  Red color lights are used for emergency purposes e.g. fire trucks and ambulance because it has long wavelength. 12 1. Electromagnetic Radiation (EMR): A form of energy that is propagated through space or matter, exhibiting both wave-like and particle-like properties, including visible light, radio waves, X-rays, etc. 2. Electromagnetic Spectrum (EMS): The range of all types of electromagnetic radiation, from gamma rays (shortest wavelength) to radio waves (longest wavelength). 3. Wavelength (λ): The distance between two successive crests or troughs of a wave, typically measured in nanometers (nm) in the context of light. 4. Frequency (υ): The number of wave cycles that pass a given point per second, measured in Hertz (Hz). 5. Photon: The fundamental particle of light, representing a quantum of electromagnetic energy. 13 6. Visible light: The portion of the electromagnetic spectrum visible to the human eye, typically ranging from 400–700 nm in wavelength. 7. Gamma rays: High-energy electromagnetic radiation with the shortest wavelength and highest photon energy. 8. Radio waves: Electromagnetic radiation with the longest wavelength and lowest energy in the electromagnetic spectrum. 9. Diffraction: The bending of light waves around obstacles or through narrow openings, causing spreading out of the wave. 10. Refraction: The bending of light as it passes from one medium to another where the speed of light is different, described by Snell's Law. 11. Reflection: The process by which light bounces off a surface and returns to the original medium. 12. Refractive Index (n): A measure of how much a material slows down light compared to its speed in a vacuum; air has a refractive index of approximately 1. 14 13. Snell’s Law: A formula used to describe the relationship between the angles of incidence and refraction, dependent on the refractive indices of the two media. 14. Scattering: The process by which small particles in the atmosphere cause light to spread out, responsible for phenomena such as the blue color of the sky. 15. Amplitude: The maximum extent of a wave, measured from its rest position to its peak or trough. 16. Wavenumber (ύ): The number of waves per unit distance, often used in spectroscopy. It is the reciprocal of wavelength, measured in cm⁻¹. 17.Transverse wave: A wave in which the oscillation is perpendicular to the direction of wave propagation, as seen in light waves. 15 18. Spectroscopy: The scientific study of how electromagnetic radiation interacts with matter, often used to study electronic transitions, vibrations, and rotations in molecules. 19. Electronic Transition: The movement of an electron between energy levels within an atom or molecule, which can absorb or emit electromagnetic radiation. Examples include n → π*, π → π*, n → σ*, σ → σ* transitions. 20. Planck’s Constant (h): A fundamental constant used to describe the quantization of energy in photons, with a value of approximately 6.626 × 10⁻³⁴ J·s. 21. Photon Energy (E): The energy carried by a photon, calculated by 𝐸=ℎ𝜈E=hν or 𝐸=ℎ𝐶/𝜆E=hC/λ, where h is Planck's constant, ν is the frequency, and λ is the wavelength. 16 21. Absorption: The process by which matter captures electromagnetic radiation, converting the energy of photons to internal energy. 22.Transmission: The passage of electromagnetic radiation through a medium without being absorbed. 23. Dual nature of light: The concept that light exhibits both wave-like and particle-like behavior, depending on the context of the observation (i.e., wave in diffraction and particle as photons). 24. Speed of light (C): A constant representing the speed at which light travels in a vacuum, approximately 3×108 meters per second (m/s). 25. Ultraviolet (UV) light: Electromagnetic radiation with shorter wavelengths than visible light but longer than X-rays, typically in the range of 10–400 nm. 17 I. Choose the correct answer: 1. What is the type of electromagnetic radiation between gamma rays and ultraviolet radiation: a. Radiowaves b. X-rays c. Microwaves d. Visible radiation 2. One of the following is not an electromagnetic radiation: a. Microwave b. Alpha c. X-rays d. Radiowaves 3. Distance between two successive crests or troughs is: a. Wavenumber b. Velocity c. Amplitude d. Wavenumber II. Complete the followings: a. Wavenumber is---------------------------------------------------------------- b. Snell's Law is------------------------------------------------------------------ c. Reflection of light is---------------------------------------------------------- d. Light has property of-----------------------------and------------------------- e. Longest wavelength is----------------------------------rays. 18 20