Fundamentals of Light and Electromagnetic Radiation.pptx

General information about the electromagnetic wave

1. Fundamentals of Light and Electromagnetic Radiation Introduction to Electromagnetic Radiation

2. Electromagnetic radiation: is a form of energy that travels through space as waves. It includes different types of waves, such as visible light, ultraviolet , radio waves, microwaves, infrared, , X-rays, and gamma rays. These waves are made up of electric and magnetic fields that move together and carry energy across space. These electric and magnetic fields are intimately connected and perpendicular to each other, with a 90-degree angle. Electromagnetic radiation doesn’t require a medium to travel ; it can move through the vacuum of space, making it different from mechanical waves like sound . This is why sunlight reaches Earth even though there is no air in space.

3. 2. Wave-Particle Duality of Light One of the most interesting characteristics of light is its wave-particle duality . This means light behaves both like a wave and a particle: As a wave , light can be described by its wavelength and frequency. As a particle , light is composed of photons . Each photon has a specific energy that is related to its frequency.

4. Basic Properties of Electromagnetic Waves Electromagnetic waves are described by several key properties: Wavelength (λ) : The distance between successive peaks or trough of the wave. It is usually measured in meters (m) or nanometers (nm) . Frequency (ν) : The number of wave cycles that pass through a point in one second. It is measured in hertz (Hz). Amplitude : The height of the wave from its midline, which is related to the intensity or brightness of the light. Speed (c) : In a vacuum, electromagnetic waves travel at the speed of light, which is approximately 3.00×10 8  m/s

5. Electromagnetic radiation travels as transverse waves, meaning that the oscillations occur perpendicular to the direction of wave propagation. This characteristic allows electromagnetic radiation to traverse space, enabling it to propagate through a vacuum, unlike other types of waves.

6. The Electromagnetic Spectrum The electromagnetic spectrum refers to the entire range of electromagnetic waves, from very short wavelengths (high energy) to very long wavelengths (low energy). Different types of EM radiation correspond to different regions of the spectrum: Gamma Rays : Extremely short wavelengths (less than 0.01 nm) and very high energy can used in nuclear reactions X-rays : Wavelengths between 0.01 and 10 nm . Used in medical imaging and in studying the structure of materials. Ultraviolet (UV) Radiation : Wavelengths between 10 and 400 nm . UV light has enough energy to cause chemical reactions. Visible Light : The narrow band of wavelengths from 400 to 700 nm that humans can see. Infrared Radiation (IR) : Wavelengths from 700 nm to 1 mm . Often associated with heat; used in thermal imaging and night vision cameras. Microwaves : Wavelengths from 1 mm to 1 meter . These waves are used in microwave ovens and for radar. Radio Waves : Wavelengths greater than 1 meter . These are used in communication, such as broadcasting television and radio signals.

7. Interaction of Light with Matter When electromagnetic radiation interacts with matter, several things can happen: Reflection : Light bounces off the surface of an object. This is why we see objects around us. Refraction : Light changes direction as it passes from one medium to another (like air to water), due to a change in its speed. Absorption : Light can be absorbed by an object, transferring its energy to the object, often resulting in heat or exciting electrons. Transmission : Light passes through an object, like glass or air, without being absorbed. Scattering : Light is scattered in different directions when it strikes small particles.

8. Energy of Electromagnetic Radiation The energy carried by a photon of electromagnetic radiation depends on its frequency and is given by the Planck's Equation : E= h v Where: E is the energy of the photon, h is Planck's constant (6.626×10 −34  J\ s ν is the frequency of the electromagnetic radiation.

9. The Photoelectric Effect: Evidence of Light’s Particle Nature The photoelectric effect is a phenomenon where electrons are ejected from a material (usually a metal) when it is exposed to light . Classical wave theory of light predicted that the energy of ejected electrons would depend on the intensity (brightness) of the light, meaning stronger light should emit more energetic electrons .

10. Why This Shows Light Behaves as Particles: The fact that the energy of the emitted electrons depends on the frequency of the incoming photons supports the idea that light delivers energy in discrete "chunks" (photons), rather than continuously as a wave. Below a certain frequency, no electrons are emitted, even if the light is very bright. This cannot be explained by wave theory, where increasing the intensity (brightness) of light should increase energy delivery, but it doesn’t.