Physics Notes PDF
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These notes provide a basic overview of light, including its properties, importance, and different types of light sources. It describes light as an electromagnetic wave, discusses the speed of light and different materials, and touches on light as a particle. The document also covers various light-emitting phenomena like incandescence, fluorescence, and luminescence. The note includes examples and types of light sources and also how light is used in a variety of applications like the properties of different light waves.
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Physics Notes 💡 What is light? Light is an electromagnetic wave. Light is a particle (photon) and a wave Light is produced when electrons are excited Importance 1. Allows for visibility 2. It provides heat and warmth 3. Provides energy required for photosynthesis Properties of Light 1...
Physics Notes 💡 What is light? Light is an electromagnetic wave. Light is a particle (photon) and a wave Light is produced when electrons are excited Importance 1. Allows for visibility 2. It provides heat and warmth 3. Provides energy required for photosynthesis Properties of Light 1. Speed of light, the airspeed is 300 000 000 m/s, and the speed of light is different in each material (Air, Water, Glass, etc) 2. Travels through a vacuum, does not need a material 3. Linear propagation Light travels in a straight line 4. Light can be reflected, absorbed and/or refracted, the change of light rays when they bounce off 5. Something, we see colour because they are reflected into our eyes and the colors are absorbed into the objects that have colour 6. Light is a form of electromagnetic energy, the energy of light waves vary Electromagnetic Wave Factors: - Wavelength, is the difference between the two peaks in a wave, (how far apart are they?) - Wave Frequency, the number of times a wave repeats itself in one second (how many waves are there in one second?) The closer (smaller) the waves are the more energy they have. The further (longer) the waves are the less energy they have Examples: Radio Microwave Infrared Visible Ultraviolet X-rays Gamma Waves s light light light rays - AM/FM - - Remote - Human - Causes - Medical - Radio Microwave Controls eyes skin and imaging Astronomy - TV signals ovens - Heat - Rainbows tan - Cancer - Cancer - Radar - detection sunburn treatment Treatment Astronomy - “black” - Product lights of nuclear decay Light Sources They can be primarily broken down into Natural and Artificial Some examples of Artificial include TV screens, LED lights, and street lights Light can also be divided into luminous and non-luminous There are 7 types of luminous objects TYPE DESCRIPTION EXAMPLE Incandescence - Production of light because of heat (Inefficient) - Heat + Light = Chemical / Electrical Energy Incandescent light bulb Fluorescence - UV radiation producing light (Efficient) - The bulb is filled with mercury vapour, and the bulb is coated with fluorescent material, when the electricity interacts with the mercury it produces UV light, and the coating enables us to observe the Fluorescent light bulbs light. → → Luminescence - The process of producing light by passing an electrical current through a gas - When electrons get excited they produce light - Light generated without heating the object Neon Signs Phosphorescence - The emission of Visible light emitted after exposure to ultraviolet light continues until the input (source) is removed. Glow in the dark Chemiluminescence - The light that is released by the energy generated in a chemical reaction - Chemical energy → Light Glow stick Bioluminescence - Light that is produced from a chemical reaction in living organisms Jellyfish Triboluminescence - The production of light from friction as a result of scratching, crushing, or rubbing certain crystals Wint-O-Green Lifesavers Luminescence - Laws of Reflection 1. The angle of incidence equals the angle of reflection 2. The incident ray, the reflected ray, and the normal all lie in the same plane Concave Mirror It caves into the object. Key Terminology: Center of Curvature (C), this is the center of the sphere that would be formed by the curve of the miroir Focal Point (F), this is the point in between the (C) and the (V) Focal length (f) this is the distance between the (F) and the (V) Vertex (V) this is where the principal axis meets the miroir Principal Axis is the line that goes through the center of curvature and the miroir, if the miroir were a circle it would be the diameter. The Rules: Focal Point Rule: F-90 Principal Axis Rule: 90-F Center of Curvature Rule: C Vertex Rule: Plane mirror Notes on the rules The Focal Point Rule and the Principal axis rule are the same except reversed. The Center of Curvature rule is useless The vertex rule is the law of reflection Scenarios: Convex Mirrors It caves out The rules are the same as the Concave mirrors the one thing to be aware of is the LOST is always the same, no matter where the source of light comes from Application Flashlight - A flashlight has a concave inside of it, the light is positioned at the focal point, thus when the light is turned it disperses in different directions. Security Mirror - This is used to create an image of an object/person that from their angle they won’t be able to see. With that mirror it allows security and people to extend their vision. For instance in a gas station to observe if there are any thieves. Makeup Mirror - This mirror is used to enhance facial features by enlarging them. They do this to make it easier and more precise to put on makeup or shave. Dental Mirror Car Headlights Solar Oven Cooker Refraction Light traveling at 0˙ will pass right through the mediums Total Internal Reflection - Light is travelling from a more optically dense medium into a less optically dense medium - The angle of incidence is larger than the critical angle to allow no refraction but only reflection n = c/v or c = n*v or v = c/n n = the index of refraction v = the speed of light in a medium (the chart) c = the speed of light in air (3.00 x 108 m/s) Applications of Refraction - Example: Dropping your phone in the water and reaching in the wrong spot - Mirages, - Rainbow’s, you need to be positioned in between the rain and the sun, what happens is, the light from the sun enters the raindrops, and refraction results in dispersion. Then partial internal reflection occurs, and then lastly the light exists the raindrop resulting in what we perceive as rainbows. Lenses Terminology: Lens Light transmits and refracts through a lens Optical Center The point at the exact center of the lens (Secondary) Principal Focus (F Prime) The common point where parallel light rays converge after refraction Three common rules are used when determining where the image is: - The principal axis rule (Goes parallel to the PA and then goes through the PF) - The focal point rule (Goes through the focal point then straight) - Optical center rule (Goes right through the middle from the top of the object) Diverging Lenses Converging Lenses APPLICATION OF LENSES DIVERGING CONVERGING Peephole Cameras Flashlight Movie Projector Magnifying Glass Compound Microscope Refracting Telescope Thin Lines Equation 1 1 1 𝑓 = 𝑑𝑖 + 𝑑𝑜 f = The Focal Length di = The distance from the produced image and the lens do = The distance from the object and the lens The do is always positive The di is only positive when it is a real number, and negative if it is a virtual image The f is only positive if it is a converging lens, and negative if it is a diverging lens Magnification Equation 𝑑 ℎ𝑖 M = - 𝑑 𝑖 + ℎ𝑜 𝑜 ℎ𝑖 = The height of the image produced ℎ𝑜= The height of the object M = Magnification The distances become negative in this equation If the Magnification > 1 then the size of the image is Bigger If the Magnification < 0 then the size of the image is Smaller M is positive when it is an upright image M is negative when it is an inverted image The Human Eye Anatomy of the Eye - Retina - Light sensitive, back of the eye and surrounded by nerves - Optical Nerve - The nerves located in the eye - Ciliary Muscle - Allows lens to change shape - Lens - Refracts light so it hits the retina - Pupil - Hole of the eye that allows light in - Iris - A ring that controls the size of the pupil - Cornea - Allows light to enter the eye - Refracts light Lens + Cornea = Generates a smaller, real, inverted image, on the retina Normal Eye Hyperopia (Farsightedness) Difficulty seeing nearby objects The distance between the lens and the retina is too small, thus forming an image beyond the retina. Myopia (Nearsightedness) Difficulty seeing far objects The distance between the lens and the retina is too large creating an Image before the retina Application of the can be compared to a camera, or a movie