UNIT C LIGHT & OPTICAL SYSTEMS PRESENTATION.pdf

UNIT C LIGHT & OPTICAL SYSTEMS SECTION 1 Our knowledge about light and vision comes from explanations, inventions, and investigations 1.1 The Challenge of Light Since the earliest times, light has been studied. The Greek Scientist Archimedes developed a plan to reflect light to burn enemy ships...

UNIT C LIGHT & OPTICAL SYSTEMS SECTION 1 Our knowledge about light and vision comes from explanations, inventions, and investigations 1.1 The Challenge of Light Since the earliest times, light has been studied. The Greek Scientist Archimedes developed a plan to reflect light to burn enemy ships. However, this has neither been proven or disproved. Recent experiments have shown that if it is true, the worst an enemy ship would receive is a small burn PYTHAGORAS Pythagoras tried to explain how we see light. He believed beams came from a person’s eyes in straight lines. When they hit the object, that object was seen. Problem: that would make the assumption you would be able to see objects in the dark. EUCLID Euclid was a Greek mathematician. He was fascinated by shape and created a new type of mathematics called geometry that described shapes and angles. Euclid wrote a book called Optiks about the geometry of light and seeing. Euclid used his observations of light in the world around him to make some predictions about light rays: - Light rays are straight lines. - You see an object in a particular direction because light rays come from that direction. PTOLEMY ❏ Ptolemy - astronomer who described that light beams bend when they go from air to glass. ❏ Today we refer to this as refraction. The Law of Refraction al-HAYTHEM ❏ al-Haytham was the first to accurately describe how vision worked and that light bounces off objects then travels to the eye - thus Pythagoras’ theory was dismissed. ❏ ❏ He was a pioneer who made many contributions to understanding vision, optics and light. He used experiments following the scientific method to draw conclusions. SIR ISAAC NEWTON ❏ Sir Isaac Newton was interested in the colors of the rainbow. He discovered that when light passes through a prism, light is split up into different colors. OLE ROEMER ❏ Galileo attempted to measure the speed of light by having two individuals stand on different hilltops. ❏ One would uncover a lantern and the other uncover there’s when they saw the light. The problem was that the speed of light was too fast and distance too short to determine the speed. Ole Roemer was able to determine the speed of light by examining the moon IO as it revolved around Jupiter. He determined it to be 227,000 km/s. Lower than the actual of 300,000 km/s. ALBERT A. MICHELSON Albert Michelson used a three-sided mirror, light source and an observer to calculate the speed of light. By spinning the mirror and using mathematics he was able to determine the speed of light to be 299,798 km/s. He presumably did this between hilltops spread great distances. Light Year A light-year is a unit of distance, not time. A light-year is how astronomer measure distance in space. It is defined by how far a beam of light travels in one year in a vacuum (space) 1 light year = 9.64 trillion miles Think of it as the bigger, badder cousin of the centimeter, meter and kilometer. Light Speed, Fast, but Slow https://interestingengineering.com/video/the-speed-of-light-this-cool-visual-shows-how-fast-but-also-slow-it-is Properties of Light ● Light travels in straight lines ● Light can be reflected ● Light can bend ● Light is a form of energy Properties of Light 1.2 Optical Devices Optical Device Any technology that uses light Simple as a mirror Complex as the James Webb Space telescope Can you think of other technologies that use light? Optical Devices ❏ Fibre optic cable ❏ Computers in pin and chip machines when you use a debit/credit card carries info through light impulses ❏ Light bulbs ❏ Solar powered devices ❏ Medicine - lasers for incisions, cameras, brain imaging ❏ 3D printing ALESSANDRO DELLA SPINA First Optical Devices ❏ ❏ 1300 A.D. and Italian Monk created the world’s first eyeglasses to correct vision. His name, Alessandro della Spina. HANS & ZACHARIAS JANSSEN It is believed that the father and son team of Hans and Zacharias Janssen of the Netherlands first built a microscope in about 1505. ANTONIE VAN LEEUWENHOEK Antonie van Leeuwenhoek (Denmark), a Dutch scientist, experimented with own microscope in the 17th Century. He looked at things like pond water, blood, and plaque from his own teeth. What he saw amazed him and called these “little animalcules”...... which was the first descriptions of bacteria, algae, and red blood cells. Thus began the study of “MICROBIOLOGY” MICROBIOLOGY Microscopes are indispensable tools in microbiology as they: ● ● ● ● ● enable visualizing microorganisms identifying species conducting research diagnosing diseases ensuring quality control in various industries Properties of Light Microscopes Uses lenses to create an enlarged image of a tiny object. Telescopes Both magnify and collect light. Magnifying power of telescopes allowed Galileo to see Venus and faint objects around Jupiter. He also saw mountains and craters on the moon. Types of Telescopes Reflecting Telescopes Refracting Telescopes (use mirrors, smaller) (use lenses and mirros, easier to use) Reflecting Telescope Refracting Telescope Reflecting Telescope Refracting Telescope - Also known as a reflector - Also known as a refractor - Uses mirrors to gather and focus light - Uses lenses to bend and focus light - More affordable due to how inexpensive mirrors are to make than lenses. - Produce sharp images - Easier to manufacture - Less maintenance required. - More compact and lighter Physics: Optics is fundamental to the study of light and its interactions with matter. It helps in understanding phenomena like reflection, refraction, diffraction, and interference. Engineering: Optics plays a crucial role in various engineering disciplines. It is used in the design and development of optical systems, such as lenses, microscopes, telescopes, lasers, fiber optics, and imaging devices. Medicine: Optics is widely used in medical imaging techniques such as endoscopy, microscopy, and optical coherence tomography (OCT). It enables non-invasive visualization and diagnosis of internal body structures. Astronomy: Optics is essential in studying celestial objects. Telescopes and other optical instruments help astronomers observe distant stars, galaxies, and other astronomical phenomena. Communications: Fiber optics is extensively used in telecommunications for high-speed data transmission over long distances. Optical fibers carry information in the form of light signals, providing faster and more reliable communication. Photography: Optics is the foundation of photography. Cameras utilize lenses to focus light onto an image sensor or film, capturing and recording visual information. James Webb Space Telescope Alpha Centauri The closest star to Earth is Alpha Centauri. The journey to Alpha Centauri would take about 100 years at an average speed of 13,411 km/s (4.5% the speed of light) and another 4.4 years would be necessary for data to reach Earth. Binoculars Binoculars are two refracting telescopes fixed together. Binoculars are not as powerful, but more convenient to use. Since they are refracting, they use refracti ng lenses. Binoculars Binoculars work by using a pair of identical telescopes side by side, which allows for a wider field of view and a three-dimensional image. The lenses in each telescope gather and focus light, which is then magnified by the eyepieces. The eyepieces allow the viewer to adjust the focus and distance between the lenses to match the distance between their eyes, creating a single, clear image. Section 1 QUIZ Make a Pinhole Camera SECTION 2. Light behaves in Predictable ways 2.1 Light Travels in Rays Depending on the situation, light will reflect, transmit, or both. Why do diamonds sparkle? Diamonds get their sparkling characteristic from three things: 1. Reflection 2. Refraction 3. Dispersion Only a portion of the light hitting a diamond is reflected The rest of the light travels through it. As the light moves through the diamond, it is scattered, creating a sparkle. Ray Diagrams Scientists use Ray Diagrams to show how light travels from a source in a straight line called a “ray”. However light travels away from a source in all directions. To show all the light rays you would have to draw millions of lines, which is not practical. These diagrams are useful to show how light behaves in specific circumstances. Ray Diagrams help explain why the brightness, intensity, of a light changes with distance. Figure 2.3 shows that the further you move from a source, the less rays hit your eyes, thus making the brightness, intensity, less. Shadows Ray Diagrams help explain shadows. When an object blocks the light, the light rays can go no further creating a shadow. Your body blocks and absorbs the light. The closer an object is to the light source, the larger the shadow it casts. This is because an object closer to the source will block a larger area of light, increasing the image size. Light Interacts with Material When light hits an object it behaves in different ways depending upon the type of material the object is made of. Transparent Materials Light can travel through the object. Translucent Materials Allows some, but not all light to pass through. The light changes directions many times and that not reflected can be absorbed and converted to heat. Opaque Materials These material do not let any light through them. Non-Luminous Opaque objects do not produce light. Luminous A light source, produces light. The reflection of light off non-luminous objects is the reason you can see them. Types of Reflection Regular (Specular) Reflection Occurs when light rays hit a smooth surface. All rays reflect at the same angle as the incoming ray. Diffuse Reflection Occurs when light rays hit a rough surface. Rays are reflected at different angles. It is easier to see a rough surface from different angles due to the diffusion of light from its surface. Smooth surfaces are not as easy to see at different angles. Think About It 1. What are some ways you can change the direction of light rays? 2. What happens to light when it hits a translucent object? 3. What would make a better reflector, a piece of wood, or a piece of metal? 4. A basketball does not give off light, then why can you see it? 2.2 The Laws of Reflection Incident Rays (incoming rays) Bounce off as a parallel beam giving a regular reflection. The shinier and smoother the surface, the better the reflection. Plane Mirrors (flat mirrors) provide the best reflective surface. Angle of Incidence - angle in degrees of the incoming light ray. Normal - imaginary line perpendicular to the plane mirror located at the point of incidence and point of reflection. Angle of Reflection - angle of the outgoing light ray. Three Laws of Reflection 1. The angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal 2. The incident ray, the normal and the reflected ray are all in the same plane 3. Incident ray and refracted ray are on different sides of the normal 2.3 Reflecting Light with Curved Mirrors World’s Largest Mirror Telescope Concave Mirrors Has a surface that curves inward like a bowl. These rays all head back to focal point. The image formed by a concave mirror is dependent on how far away the object is from the focal point (f). ● ● ● If far away the image is small & upside down. As the object moves closer to the focal point it remains upside down but gets larger If image is between focal point and mirror it becomes upright and larger Concave Mirrors Simulation Click here to access the link Magnifying Lens Activity Applications of Concave Mirrors Convex Mirrors Has a surface that curves outward. Convex mirrors are curved outwards, which causes light rays to diverge or spread out when they hit the surface of the mirror. This results in a wider field of view, but also causes objects to appear smaller and farther away than they actually are. Additionally, the distortion in the shape of the mirror causes the reflected image to be distorted, making straight lines appear curved and changing the proportions of objects in the reflection. Ray Box LAB 2.4 Transparent Substances Refract Light Law of Refraction When light travels from one medium, to a more dense medium, the light will be bent toward the normal, and when it exits the denser medium into a less dense medium it will bend away from the normal. When light travels from one medium, to a more dense medium, the light will be bent toward the normal. When it exits the denser medium into a less dense medium it will bend away from the normal. Fill a beaker halfway with water. If you fill it too much, the bend is not as apparent. Play around with different levels of water to see how light influences refraction. Light refraction occurs when something gets in the way of light waves. Because the light can’t travel as quickly in water as it does in the air, the light bends around the pencil/pen. Light refraction gives the pencil a slight magnifying effect, which make the angle appear bigger than it actually is, causing the pencil to appear crooked. The denser the medium, the more the light slows down, thus the more it refracts. A fish in the water is not where it appears to be. The problem is that light bends when it leaves the water. When a light ray strikes a boundary where two different substances meet (often referred to as the interface) at an angle, it will change direction. The actual fish is below and in front of the image. Mirages 2.5 Lenses Refract & Focus Light Concave Lenses Convex Lenses Why are they important? ❏ Collect light like a concave mirror ❏ A convex lense forms a real image meaning light rays meet and can be projected onto a screen ❏ ❏ ❏ ❏ ❏ Curves outward. Is referred to as a double convex lens if both sides curve outward. Light ray when they pass through the convex lens refract to a single point (focal point) and cross. If you fill it too much, the bend is not as apparent. Play around with different levels of water to see how light influences refraction. Image Formation - Convex Lenses Play around with different levels of water to see how light influences refraction. A Image formation depends on distance of object from the lense. B If the object is farther away from the focal point, the image formed is upside down. C Image will appear upright if in between the focal point and lense. Section 2 QUIZ 3.0 Light is part of the electromagnetic spectrum and travels in waves 3.1 The Wave Model of Light The Wave Model of Light pictures light traveling as a wave. Properties of Waves amplitude—the height of a wave from the rest position to the crest (highest point) wavelength—the distance from the crest of one wave to the crest of the next frequency—the number of times the medium vibrates in a given unit of time Trough—lowest point on a wave. Crest - highest point on a wave. Waves with shorter wavelengths have higher energy than those with longer wavelengths. Formula Speed = wavelength x frequency Ex. 10 cm x 5 Hertz (seconds) 50 cm / s Visible Light Spectrum Visible light waves are the only wavelengths of the electromagnetic spectrum that humans can see. The different wavelengths of visible light are seen as the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. The longest wavelengths (around 700 nanometers) are red and the shortest wavelengths (380 nanometers) are violet. Click for Interactive Spectrum 3.2 The Electromagnetic Spectrum The electromagnetic spectrum describes all of the kinds of light, including those the human eye cannot see. In fact, most of the light in the universe is invisible to our eyes. Click for Interactive Spectrum Video Click for Interactive Spectrum White light is made up of different colors of light, each with a different wavelength and frequency. When white light passes through a prism, it is refracted (bent) at different angles depending on its wavelength. This causes the different colors of light to separate and spread out, creating a rainbow-like spectrum of colors. The Electromagnetic Spectrum Poster Project 3.3 Producing Visible Light The Uses of Light Doctors use both light that is visible in ❏the electromagnetic spectrum, and that which is not. ❏ ❏ ❏ Visible light is used in endoscopy Lasers used to make incisions X-rays used to view dense structures and tissue of our body ❏ Gamma rays used to shrink enlarged tissues. These are all a part of the Electromagnetic Spectrum Radiant Energy Light is a form of energy you can see. This energy can be produced naturally (sun) or artificially by technologies including batteries and light bults. The Light Bulb ❏ ❏ ❏ ❏ Thomas Edison began experimenting with incandescent light bulbs in 1878. Experimented with a number of organic materials to finally find that bamboo threads had the greatest resistance to heat and could glow for up to 30 hours. However, these were no brighter than a candle. Finally tungsten was used in the 1900s which lasted longer and were much brighter. Artificial Sources of Light ❏ Incandescent Lighting -electricity flows through the wire heating it to extreme temperatures causing the wire to glow. -loses 85% of its energy through heat loss. ❏ Fluorescent Lighting - glass tube filled with a gas vapour, with the inside covered in a white powder called phosphor - as electricity passes through the gas is ignited producing ultraviolet radiation. - the ultraviolet radiation strikes the phosphor (mercury) which then glows and emits white light. Incandescent Bulb Inert gas—gases that do not go through a chemical reaction (argon prevents the filaments from deteriorating too quickly). Tungsten filament—an alloy wire made from tungsten and other metals that produces light when it is heated. Fluorescent Bulb A fluorescent bulb is a glass tube filled with a small amount of a gas such as mercury vapour. The inside of the bulb is coated with a white powder called phosphor. Electricity passes through a fluorescent bulb many times per second. Each time it passes through, it makes the gas in the bulb emit ultraviolet radiation. This ultraviolet radiation strikes the phosphor on the inside of the bulb, which then glows and emits visible white light. The emission of white light in this way is called fluorescing. Phosphorescent Lighting -similar to fluorescent lights; however, they they have the ability to glow after the energy source has stopped. - This ability to glow after is referred to as phosphorescence. LED Lighting (Light Emitting Diodes) - uses a number of diodes in one light - do not use a filament, instead a semiconductor material in which the electrons are charged to create light. - they use 85% less energy - can last up to 15 years - An electrical current passes through a microchip, which illuminates the tiny light sources we call LEDs and the result is visible light. Chemiluminescence Lighting Chemiluminescence (CL) describes the emission of light that occurs as a result of certain chemical reactions that produce high amounts of energy lost in the form of photons when electronically excited product molecules relax to their stable ground state. Types of Lighting PDF (click to the right) Natural Sources of Light ❏ - Bioluminescence When a living organism produces its own light. Can you think of any? The light of a firefly is a chemical reaction caused by an organic compound – luciferin – in their abdomens. As air rushes into a firefly's abdomen, it reacts with the luciferin. Consequently, it causes a chemical reaction that gives off the firefly's familiar glow. The organ that produces the light is called the photophore. Natural Sources of Light ❏ Bioluminescence Play around with different levels of water to see how light influences refraction. Firefly Firefly Squid Chemiluminescence Demonstration Research Project (in Google Classroom) Your task is to research a bioluminescence organism. The following must be produced in Google Slides and contain the following information: What is the organism? Where does it live? How does it create its bioluminescence? Life span? Food Source? And……………………………………. Any other information you can find. 3.4 The Color of Light Producing White Light The production of white light by combining all the colours of the visible spectrum can be simplified. All you really need to produce white light are three colours: red, green, and blue. These three colours are known as the primary colours. This new colour is called a secondary colour. These are magenta, yellow and cyan. Televisions The television works by fooling the eye into seeing colours that are not really there. If neighbouring blue, red, and green dots glow, the eye will see white. If neighbouring red and green dots glow, you will see yellow. As the neighbouring dots glow in different combinations, the screen can produce all the secondary colours. By changing the brightness of each dot, the screen can produce a wide range of colours. Section 3 QUIZ 4.0 Human Eyes 4.1 Image Formation in Eyes With the ability to distinguish about 10 million different colors and the ability to perceive depth, the eye is one of the most complex organs in the human body. How the Human Eye Works optic nerve - nerve transmits electrical impulses from your eyes to your brain. Your brain processes this sensory information so that you can see. retina - special layer at the back of the eye containing ‘photoreceptors’ (rods and cones) used to function in low light conditions and see colour. There are three types of cone cells: red, green, and blue. ciliary muscle - muscle that changes the shape of the lens to allow you to focus on objects. iris - circular band of muscle that creates the opening for the pupil. cornea - The transparent part of the eye that covers the iris and the pupil and allows light to enter the inside lens - convex lens used to focus light onto the retina.. pupil - hole through which light enters the eye. The human eye and brain work together to convert visible light energy into an electrical impulse that can be interpreted as an image. When focusing on an object, the cornea, iris, and pupil help light enter the lens of the eye. The lens bends the light so the image is turned upside down and projected onto the retina at the back of the eye. This stimulates the retina’s photoreceptors, called rods and cones. Cones detect color and fine details in high light conditions. In low light conditions, rods detect grays and movement. rods cones The rods are more numerous, some 120 million, and are more sensitive than the cones. However, they are not sensitive to color. Rods help you see in low light conditions. The 6 to 7 million cones provide the eye’s ability to see colour. Overwhelming Your Cones How Light Gets In - - Light passes through the outer layer of the eye called the cornea The light then enters through the pupil which is not really there (like a donut hole) created by the iris The iris - Determines your eye color - Amount of light that enters your eye In dim light, the iris opens and the pupil dilates (becomes wider) to let in more light. In bright light, the iris closes and the pupil constricts (becomes smaller) to let in less light. Changes in pupil size happen automatically; you don’t have to think about it. When Light Gets Inside When light strikes the retina, photoreceptors are stimulated, and they send messages to the optic nerve which passes the message to the brain. Photoreceptors include: Rods - highly sensitive to light thus being able to function in very low light conditions Cones - detect color and do not function well in low light resulting in seeing only shades of grey When Light Gets Inside When light strikes the retina, photoreceptors are stimulated, and they send messages to the optic nerve which passes the message to the brain. The brain translates the message into an image. 3D INTERACTIVE Focusing the Light ❏ ❏ ❏ ❏ ❏ ❏ The lens of your eye must be in the right position in order to produce a sharp image. Muscles attached to the lens (ciliary muscles) relax or contract to change the shape of the lens. Changing the shape of the lens adjusts the focal length so that light forms a focussed image on the retina. In automatic cameras the lens moves back and forth automatically in order to produce a sharp image. On manual cameras this is done by hand. The images formed are upside down. Ciliary muscles contract to lengthen the lens and relax to shorten the lens. Focusing the Light ❏ Although the image formed on the retina is upside down, your brain corrects for this and interprets the world as right side up. Optic Nerve & The Brain When light falls on the retina it is transmitted as electrical impulses to the optic nerve and from there to the brain where the upside-down 2D image is processed into a right-side up, 3D image. The incoming electrical impulses are separated and analyzed in different parts of the brain. The separation begins in the retina and continues as visual information flows through all four lobes of the brain where it is analyzed for color, movement, size, distance, and other visual features. Correcting Vision Most eye problems fall into two categories: Play around with different levels of water to see how light influences refraction. 1. Farsightedness (Hyperopia) Can see objects far but cannot see close objects clearly. The eye cannot make the lense flat enough to focus light on the retina. The image ends of falling behind the retina. 2. Nearsightedness (Myopia) Cannot see distant objects clearly. The eye cannot make the lens thin enough to focus light on the retina and image falls in front of the retina. 3. Astigmatism Cannot see distant objects nor close objects clearly due to an imperfection in the curvature of the eye. Laser Eye Surgery In laser eye surgery, surgeons use a laser to reshape the cornea of the eye. Play around with different levels of water to see how light influences refraction. Night Vision Goggles ❏ ❏ ❏ ❏ Light is focused onto an image intensifier. Inside the intensifier, the light energy releases a stream of particles. These particles hit a phosphor-coated screen. The phosphors glow green when the particles strike them. ❏ ❏ Light is focused onto an image intensifier. Inside the intensifier, the light energy releases a stream of particles. ❏ ❏ These particles hit a phosphor-coated screen. The phosphors glow green when the particles strike them. 4.2 Other Eyes in the Animal Kingdom Do animals have the same eyes as humans? Camera Eyes ❏ ❏ Invertebrates (backbone) have camera eyes much like humans. Camera eyes have a retina, cornea, and lens and are roughly round in shape. ● ● ● ● Fish have perfectly round lenses Lens bulges out through the pupil As a result they can see in all directions Since they have no neck to turn their head, this allows them to see danger coming. Play around with different levels of water to see how light influences refraction. Fish Birds ❏ ❏ ❏ Birds have sharper vision than humans. Humans have three types of cones, birds have five. Birds can distinguish many more colors and shades than humans. Owls & Cats ❏ ❏ ❏ ❏ Cats and owls are nocturnal. Their eyes collect as much light as possible to allow them to see better in the dark. They have a layer inside their eyes called the tapetum lucidum (acts as a mirror to reflect light inside the eye) Because they need to travel in low light conditions, nocturnal animals have more rods than cones in their retinas. Remember rods are far more sensitive to light than cones. Compound Eyes ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ Insects and crustaceans (shrimp, lobsters, crayfish) have compound eyes. Each eye is made up of smaller units. Each individual unit is called a ommatidium. Insect eyes have a convex surface. This allows them to see in all directions. Detection of a change in light is very responsive. For example, trying to swat a fly, it is difficult because its sensitivity to light allows it to move quickly out of the way. Cons: ❏ Cannot see a single clear image. ❏ The image is made up of small dots of light. ❏ Referred to as a “mosaic image”. ❏ Ants have very few ommatidium, while a dragonfly has 10,000. Sheep Eye Dissection Section 4 QUIZ UNIT Final Exam