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Physics 7 - Light (characteristics, properties, kinds and types of light)
- 3. DISPERSION • Rainbows are formed through dispersion. • This happens when sunlight passes through raindrops. • A double rainbow occurs when the light is reflected twice in the drop. • The second rainbow is fainter and more pastel in tone than the primary rainbow because more light escapes from two reflections compared to one. • A key feature of double rainbows is that the color sequence in the second rainbow is reversed.
- 4. Here starts the lesson! VISIBLE LIGHT
- 5. Learning Objectives ● describe the characteristics, sources, and behaviors of light, ● relate color and intensity to frequency and wavelength, ● Perform online simulations to test the characteristics of light. ● appreciate the importance of light
- 6. ACTIVITY Color Spectrum Frequency (x1012 /s) Wavelength (x10-9 m) Frequency x Wavelength (m/s) Red 422 700 (422 x1012/s) (700 x10-9m) = 295 400 x103 m/s ≈ 3x108 m/s Orange 480 635 Yellow 510 590 Green 540 560 Blue 580 520 Indigo 610 490 Violet 670 450 ≈ 3x108 m/s ≈ 3x108 m/s ≈ 3x108 m/s ≈ 3x108 m/s ≈ 3x108 m/s ≈ 3x108 m/s
- 8. White light is made up of all the colors of the rainbow. How do we know? Because a prism splits the light into its component colors. White Light
- 9. DISPERSION • The separation of light into colors. • This creates the colors of the rainbow. • These band of colors are named as spectrum.
- 10. Visible Light • The difference between one color and another color is due to the differences in wavelengths or frequencies. • Each color has its own frequency and wavelength. Increasing wavelength VIBGYOR Increasing frequency ROYGBIV
- 11. The colors of the stars are a result of the thermal radiation from the surface of the stars. -oldest stars -coolest stars – low frequency means low energy Red Stars -youngest stars -hottest stars – high frequency means high energy Blue/White stars Colors of Objects
- 12. Color is the way our eyes perceive different wavelengths of light. It's what makes objects look different from one another. Color
- 13. Mixing colors A prism is a special glass or plastic object that can bend, or refract, light.
- 14. Unlike pigments, the primary colors of light are red, green, and blue. The secondary colors are: green + blue = cyan blue + red = magenta red + green = yellow When you combine the primary colors of light: red, green, and blue, they will reflect white light.
- 15. SOURCES OF LIGHT
- 16. SOURCES OF LIGHT Natural Sources - light are those that emit light without any human intervention or manipulation. Artificial Sources - This refers to light produced by human-made sources, such as electric bulbs, LEDs, fluorescent lights, etc
- 17. TYPES OF LIGHT Luminous - Objects that emit light on their own. Nonluminous - Objects that do not emit light of their own.
- 18. Types of Lighting • It has a thin wire coil made up of tungsten. • Incandescence means emission of light as a result of heating of the filament. Incandescent Light • Less than 10% of the energy is given out as light, the rest of its energy is given off as heat or infrared rays.
- 19. Types of Lighting • It uses the process called fluorescing. • Fluorescent lights contain gas (ex. Mercury gas) that emits ultraviolet rays when an electric current pass through the bulb. Fluorescent light
- 20. Types of Lighting • It is made up of neon gas sealed in glass tube. • When an electric current pass through the neon particles of the gas, it absorb energy until it cannot anymore hold the energy, it is now released in the form of light. Neon Lights
- 21. Types of Lighting • A type of lighting that uses small amount of solid sodium and some neon, and argon gases. • The particles of sodium vapor give off energy in the form of yellow light. Sodium Vapor Light • are commonly used for street lightings since they require very little electricity to give off a great deal of light.
- 22. Types of Lighting • a type of chemiluminescence • Bioluminescence is a "cold light." Cold light means less than 20% of the light generates thermal radiation, or heat. • Luciferin is the compound that actually produces light. Bioluminescence Offensive Adaptation – use to lure or search for prey. 1 Anglerfish Loosejaw
- 23. Types of Lighting Bioluminescence Attraction – Fireflies uses light to attract mates. Male fireflies have more flashing lights than females. 2 • a type of chemiluminescence • Bioluminescence is a "cold light." Cold light means less than 20% of the light generates thermal radiation, or heat. • Luciferin is the compound that actually produces light.
- 24. Types of Lighting Bioluminescence Changes in the environment – Organisms (bioluminescent algae) can emit light when they are disturbed. They signal a drop of salt content (salinity) in water. 3 • a type of chemiluminescence • Bioluminescence is a "cold light." Cold light means less than 20% of the light generates thermal radiation, or heat. • Luciferin is the compound that actually produces light.
- 25. TYPES OF LIGHT Luminous - Objects that emit light on their own. Nonluminous - Objects that do not emit light of their own.
- 26. Brightness - is qualitative and is dependent on the person’s perception. - depends on the source and the distance from the source.
- 27. Brightness - can be measured using luminous intensity and expressed with a unit known as candela (cd). Illuminance – the measure of the amount of light that illuminates a surface area.
- 28. Intensity - The quantity that measures the amount of light. The intensity depends upon the amount of light that passes a certain area.
- 29. Intensity defined to be the power per unit area, and it has the units of Watt per square meter (W/m2). Intensity=Power/Area or I = P/A Where: I= Intensity P= Power (Watts) A= Area of sphere (4 π r2) Π= 3.14 r = radius
- 31. SLIDESMANIA.COM - Jennifer Leban & Omar López Why do you feel hotter when you wear dark- colored clothes?
- 32. • One way solid objects are classified is by how much light is allowed to pass through that object. • A transparent object lets all of the light pass through. • A translucent object lets some light pass through. • An opaque object lets none of the light pass through. transparent next translucent opaque
- 33. SLIDESMANIA.COM - Jennifer Leban & Omar López Effects of Different Materials on Light
- 34. This window is transparent. You can clearly see the image on the other side because all of the light is passing through. This lampshade is translucent. Some of the light passes through, but not all of it. The computer is opaque. No light is passing through, so you cannot see anything behind it. However, the screen is transparent. That is why you can clearly see the man’s face behind the screen. This sphere is transparent. You can clearly see the man inside. The man, of course, is opaque. These pens are translucent. Enough light passes through to allow you to see some of the inside, but not enough to see everything clearly. next The brick wall is opaque. You cannot see any part of the boy through the wall. Decide if they are mostly transparent, translucent or opaque.
- 35. What happens when light strikes an object? • absorbed: transferred to the object (mainly as heat) • reflected: it bounces off (such as with a mirror) • transmitted: goes through (such as with glass) More about Light
- 36. One of the properties of light is that it travels in a straight line, unless it is acted on by some external force or condition. When interfered with, the path of light rays can be bounced or appear to be bent away from the original object making it seem larger or smaller than it really is.
- 37. When light strikes a surface and is redirected back to its point of origin, this is reflection. - The bouncing back of light from the surface it hits. Smooth, shiny surfaces that absorb very little light, will reflect light in almost the exact way that the light hits it. next Reflection Smooth, shiny surface
- 38. Light beams Mirrors reflect images of objects because light rays bounce off the object. The light rays travel in a straight line to a mirror, bounce off the mirror, and then travel back to the eye of the observer. next Mirror
- 39. Reflection Incident Ray - the ray of light that comes from the light source and approaches the mirror. Angle of Incidence - the angle formed by the incident ray and the line perpendicular to the surface of the mirror (normal line). Reflected Ray- the ray coming from the mirror as a result of reflection. Angle of Reflection - is the angle formed by the reflected ray and the normal line.
- 40. Reflection Laws of Reflection (For any mirror) 🔶The angle of incidence is always equal to the angle of reflection. ∠i = ∠r 🔶The incident ray, Normal and reflected ray all lie on the same plane. They all join at a point known as the point of incidence.
- 41. If the wavelength reflected by the object is green, the color perceived by the human eye is green. If the wavelength reflected by the object is black, the object absorbs all wavelengths. If the wavelength reflected by the object is white, the object reflects all wavelengths.
- 42. SLIDESMANIA.COM - Jennifer Leban & Omar López Regular Reflection - also known as specular reflection - happens when light is reflected off smooth surfaces -reflected light rays are in an orderly pattern Diffused Reflection -occurs when light is reflected off rough surfaces -reflected rays are scattered in all directions TWO MAIN TYPES OF REFLECTION
- 43. Light slows down as it goes from space to air. It slows down even more in water and glass. Why? The atoms get in the way. We use lenses to curve light on purpose. (A lens is a clear, curved transparent object used to bend light.) Light and Refraction
- 44. Convex (or positive) lenses converge (or focus) light and can form images. light source Concave (or negative) lenses diverge (or spread out) light rays. light source
- 45. Decide whether each object below best represents reflection or refraction. reflection refraction next reflection refraction reflection refraction reflection refraction reflection refraction reflection refraction
- 46. Properties of Light SCATTERING • As the light coming from the sun travels through Earth’s atmosphere, the dust particles and air molecules in the atmosphere scatter the light in all directions. • This is also known as Rayleigh scattering.
- 47. Properties of Light SCATTERING • At daytime, since blue and violet has the highest frequency and short wavelength, they are scattered and reflected to earth, so the sky looks blue.
- 48. Properties of Light SCATTERING • At late afternoon, since most of the blue and violet light is being scattered, red having the longer wavelength and low frequency is the most predominant color left when light from the sun reaches your eyes.
- 49. Properties of Light SCATTERING • Water vapor (clouds) scatter all colors equally making them appear white. • When clouds gets thicker, they absorb much of the light, allowing light not to pass through. The result is a darker cloud.
- 50. Properties of Light POLARIZATION • The process of transforming unpolarized light into polarized light. Unpolarized light Polarized light A light wave that is vibrating in more than one plane. A light wave in which the vibrations occur in a single plane. • Polaroid is a filter that will allow light to pass through that vibrates in one plane and it comes out as polarized light. • Polaroid reduces the glaring effect of light.
- 51. If light strikes a boundary between two transparent materials at the correct angle, all the light gets reflected. outside material inside material This is how fiber optics works, in a process called “total internal reflection.” Total Internal Reflection
- 52. Laser = light amplification by stimulated emission of radiation Lasers use one wavelength of light, so that all the crests and troughs are lined up (or “in step”). This way, they do not interfere with each other and spread out, like white light in a flashlight. Lasers are used for welding, cutting materials (metals, biological tissue), reading/writing CDs, transmitting data through space or optical fibers, or simply as pointers. Lasers
- 53. Visible light is also used to transmit high-speed data. Endoscopes use fiber optics to allow doctors to see internal organs and vessels. Humans see objects in the visible light spectrum. APPLICATIONSOFVISIBLELIGHT VISION MEDICINE COMMUNICATIONS
- 54. ASSESSMENT. Use ¼ sheet of paper Identification 1. What is the color of the longest wavelength in visible light wave? 2. Which visible light has the highest frequency? 3. The longer the wavelength, the ________ frequency. Essay. Briefly describe the following: 1. Color vs Intensity vs Brightness 2. Sources of light and give 1 example for each.
- 57. Color Blindness • There are two photoreceptors in the eye: Rods Cones - Work at very low levels of light. - Rods are for night vision - Used to see colors. Require more light. - Cones are for color vision.
- 58. Color Blindness Cones Blue Cone Green Cone Red Cone
- 59. Color Blindness • Different types of Color Blindness. Dichromacy The absence of one cone. 1. Protanopia – absence of red sensitive pigment cone (red-blind) 2. Deuteranopia – absence of green sensitive pigment cone (green-blind) 3. Tritanopia – absence of blue sensitive cone (blue-blind)
- 60. Color Blindness • Different types of Color Blindness. Anomalous Trichromacy A deficiency in one of the pigments. 1. Protanomaly – red weakness 2. Deuteranomaly – green weakness 3. Tritanomaly – blue weakness Achromatopsia “no color” People with achromatopsia sees only black, white and shades of gray.
Editor's Notes
- Electromagnetic Wave can travel without a medium Components of Electromagnetic Spectrum Radio, Micro, Infra, Visible, Ultra, Xray, Gamma Shortest wavelength , higher frequency – Gamma – highest energy Longest wavelength, lower frequency – Radio – lowest energy
- Have you seen a rainbow? When does a rainbow usually happen? what does the rain have to do with it? Talk about dispersion, refraction, reflection, behaviors of wave Rain drop act as a prism Dispersion – a phenomenon in which a prism separates white light into its colors. Rainbow Simulator | NOAA SciJinks – All About Weather Now where do this wave belong in the em spectrum? Visible light!
- The teacher will group the students by 4 according to their proximity, provide clear instructions, then give an activity sheet to each group. The students are given 5 minutes to solve. Which color registers the highest frequency? Shortest wavelength? Ans: Violet Which color registers the lowest frequency? Longest wavelength? Ans: Red What do you observe with the wavelength and frequency of the different colors? Ans: The wavelength decreases as the frequency is increased What did you observe with the product of wavelength and frequency for each color? What is the significance of this value? The product of frequency and wavelength in all color lights is constant and equal to the speed of light in vacuum. What can you say about the speed of the different colors of light in air? Ans: The speed of all color light in air is constant and is equal to the speed of visible light. Q6. Give a plausible explanation as to why white light separate into different colors. Ans: White light separates in color light due to the process known as dispersion. As white light enters theair glass interface, different color light exhibit different refractive indices thus separates into the visible colorlights As we go through our discussion, take note of their intensity
- So, what do you think causes a rainbow? Well, raindrops in the air act like tiny prisms. Light enters the raindrop, reflects off the side and then exits the drop. During this process, the light is broken into a spectrum, just like it is in a triangular glass prism.
- occupies a narrow range of the overall electromagnetic spectrum. Each individual wavelength in the visible light represents a particular color. Our eyes perceive different wavelengths of light, thus this narrow band of light is known as ROYGBIV. When white light passes through a prism, it is separated into its constituent colors.
- When light shines on an object, some of the light is absorbed, and some is reflected back to our eyes. The colors we see are the result of the reflected light.
- We already know that white light is actually made up of many colors? When you shine white light, like sunlight or light from a flashlight, through a prism, it splits into different colors and creates a beautiful band of colors. This is called a spectrum.
- luminou Best examples are the sun, stars, light bulb. Nonlumi but are visible because they reflect light Examples: moon, the ground and all other objects (wood, plastic and metal) we see that do not emit their own light.
- When the filament gets hot enough, it gives off red light. As it gets hotter, the filament begins to give off violet light until it combines all the frequencies of light which produces white light. Incandescent - Examples of incandescent sources are candles and incandescent bulb. These objects when heated emit both infrared and visible light.
- When the ultraviolet waves hit the powder coating inside the tube, the coating emits visible light. Luminescent - light can be produced by accelerating charges in a luminescent material such as fluorescent tube light and electric bulb.
- Different neon lights are produced by different gases. Sometimes the gases are put into colored glass tube to produce other colors. Gas Discharge Sources - electricity passes through certain gases at very low pressure to produce light like neon lamp and sodium lamp.
- When the neon ang argon gases are heated, they begin to glow. This glow heats up the sodium, causing it to change from solid into gas.
- which is simply the term for a chemical reaction where light is produced.
- luminou Best examples are the sun, stars, light bulb. Nonlumi but are visible because they reflect light Examples: moon, the ground and all other objects (wood, plastic and metal) we see that do not emit their own light.
- The closer you are to the source, the brighter the light.
- Luminous intensity - a measure of the radiant power emitted by any source of light in a given direction and is dependent on the wavelength of light being emitted. It is weighted to the sensitivity of the human eye, by what is called the standard luminosity function. Photometer – a special instrument that can be used to measure luminous intensity It indicates how bright a flat, diffuse surface appears based on the reflected light. lluminance is the measure of the amount of light that illuminates a surface area. It's often referred to as the brightness of light falling on a surface and is measured in units of lux (lx), which represent lumens per square meter. So, illuminance tells us how bright a surface appears to an observer, based on the intensity of the light falling on it.to the source, the brighter the light.
- Light intensity refers to the strength or amount of light produced by a specific lamp source. Light intensity it is the measure of the wavelength-weighted power emitted by a light source. Intensity is the absolute measure of a light wave’s power density while brightness is the relative intensity as perceived by average human eye.
- Light intensity refers to the strength or amount of light produced by a specific lamp source. Light intensity it is the measure of the wavelength-weighted power emitted by a light source. (distance of light source from the center of sphere) Intensity is the absolute measure of a light wave’s power density while brightness is the relative intensity as perceived by average human eye.
- How does light travel? In a straight line Light travels in straight path. Although light follows a straight path from the source, it can be slowed down and scattered by objects placed in its path. Light travels a speed of 300 million m/s in a vacuum (empty space). At this amazing speed, light from the sun takes only 8 minutes to travel to Earth. Light travels fastest in an empty space followed by gas, liquid and solid. Light can pass through, bounce off, or be absorbed by matter.
- When light moves through the air, it may encounter a barrier or a medium that it may pass through. It can be mirrored, absorbed, or transmitted when light enters a medium like an object. Dark-colored objects are better absorbers of light than light- colored ones. An ideal black object absorbs all the light that falls on it. When an object absorbs light, the object becomes warmer due to the energy it absorbs. Some of the energy from the light is transformed into thermal energy which is passed on as heat. The effects of different materials on Light Unlike mechanical waves (sound and water waves), light does not need a medium to be transmitted, but it can travel or pass through a medium, depending on the medium! With that, objects can be classified by the way they interact with light…
- Objects are classified by what they do to light: opaque: Does not allow light to pass through. All light is either absorbed or reflected. translucent: Can be seen through, but not clearly. Allows some light to go through, but some is also absorbed or reflected. (such as waxed paper) transparent: Allows almost all light to go through, so can be seen through clearly. (such as window glass) Objects can be classified by the way they interact with light. Materials that allow most of all light to pass through them are called TRANSPARENT It means more light passes through them. Examples of transparent items are glass, water, and air Some materials that allow some light to pass or transmit too little light through them are called TRANSLUCENT which includes frosted glass or bulbs, wax paper, and colored cellophane. If an object does not allow any light to pass through it, then it is OPAQUE Opaque materials do not transmit light, thus, you cannot see objects through them. Some examples of opaque materials include things made of wood, stone, and meta
- Ask examples Materials that allow most of all light to pass through them are called TRANSPARENT It means more light passes through them. Examples of transparent items are glass, water, and air Some materials that allow some light to pass or transmit too little light through them are called TRANSLUCENT which includes frosted glass or bulbs, wax paper, and colored cellophane. If an object does not allow any light to pass through it, then it is OPAQUE Opaque materials do not transmit light, thus, you cannot see objects through them. Some examples of opaque materials include things made of wood, stone, and metals Transparent Water, Glass, Air Translucent Frosted Window, Parchment Paper Opaque Most things
- Every second of every day our eyes detect and interpret rays of light – whether that light is coming from a natural source like the sun, or an artificial source like a lamp. However, sometimes our eyes can be fooled by the reflection and refraction of light. Now what are these phenomena?
- 2. We can see objects when they reflect light, and the reflected light enters our eyes. 3. Most objects reflect some light and absorb the light that is not reflected. Meaning, how fast or how bright it was, it would still be the same after it hit the shiny surface.
- Best example for these shiny, smooth surfaces are…
- The relationship between the angle of incidence() and the angle of reflection (0r) is given by the law of reflection: This means that the angle of incidence is always equal to the angle of reflection.
- Two types of reflection are: regular: When an object surface is smooth, and you see an image. Example: a plane (flat) mirror diffuse: When a rough surface scatters light in many directions, and no image appears. Example: paper is rough enough to scatter light so there is no image Regular reflection-Examples are from mirrors or any other surface that produces a reflected image Diffused – ex , any surface that we can see but does not reflect an image
- When the path of the light rays change directions and appear to bend as they pass through an object, we call this refraction. Refraction occurs when light passes from one substance to another of a different density (for example, from air to water). The amount of refraction depends on the angle that the light enters the new substance and the difference in the densities of the two objects. The greater the angle, the more the light ray will be bent.
- Total internal reflection allows the transmission of light-carrying information to travel great distances over curved paths.
- So with all that, how do we apply light in our life man? What will happen to Earth without light? Without the light that the sun produces the Earth will be in a total darkness and coldness. Without it there will be no life on Earth, because it is the one that sustain life on Earth. Without the artificial sources of light at night, it would be hard for us to see things. It will be difficult for us to navigate at night. What practices you must do to avoid the harmful effects of the sun? How about to protect your eyes?
- Emphasize the importance of light and encourage students to take care of their eyes. Light is like the people around us specially our parents/ our family. They are remarkable yet we sometimes take them for granted. There are times that we prefer to be with our friends than to be with them knowing that they are always there. But when the dark times of our lives come, they are first person who will help us. Or worst when they are no longer around, only then you will realize how important they are to you. Just like light, you only see its worth when darkness comes.