Physics 7 - Light (characteristics, properties, kinds and types of light)

This is educational subject about light

1. Electromagnetic Spectrum Let’s Recall

2. 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.

3. Here starts the lesson! VISIBLE LIGHT

4. 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

5. ACTIVITY Color Spectrum Frequency (x10 12 /s) Wavelength (x10 -9 m) Frequency x Wavelength (m/s) Red 422 700 (422 x10 12 /s) (700 x10 -9 m) = 295 400 x10 3 m/s ≈ 3x10 8 m/s Orange 480 635   Yellow 510 590   Green 540 560   Blue 580 520   Indigo 610 490   Violet 670 450   ≈ 3x10 8 m/s ≈ 3x10 8 m/s ≈ 3x10 8 m/s ≈ 3x10 8 m/s ≈ 3x10 8 m/s ≈ 3x10 8 m/s

6. 11 VISIBLE LIGHT

7. 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

8. DISPERSION The separation of light into colors. This creates the colors of the rainbow. These band of colors are named as spectrum.

9. 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

10. 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

11. Color is the way our eyes perceive different wavelengths of light. It's what makes objects look different from one another. Color

12. Mixing colors A prism is a special glass or plastic object that can bend, or refract, light.

13. 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.

14. SOURCES OF LIGHT

15. 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

16. TYPES OF LIGHT Luminous - Objects that emit light on their own. Nonluminous - Objects that do not emit light of their own.

17. 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.

18. 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

19. 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

20. 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.

21. 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

22. 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.

23. 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.

24. TYPES OF LIGHT Luminous - Objects that emit light on their own. Nonluminous - Objects that do not emit light of their own.

25. Brightness is qualitative and is dependent on the person’s perception. depends on the source and the distance from the source.

26. 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.

27. Intensity - The quantity that measures the amount of light. The intensity depends upon the amount of light that passes a certain area.

28. 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  

29. BEHAVIORS OF LIGHT

30. Why do you feel hotter when you wear dark- colored clothes?

31. 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

32. Effects of Different Materials on Light

33. 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.

34. 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

35. 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.

36. 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

37. 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

38. 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.

39. 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.

40. 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.

41. 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

42. 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

43. 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

44. Decide whether each object below best represents reflection or refraction. reflection refraction next reflection refraction reflection refraction reflection refraction reflection refraction reflection refraction

45. 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.

46. 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.

47. 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.

48. 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.

49. 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.

50. 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

51. 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

52. 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. APPLICATIONS OF VISIBLE LIGHT VISION MEDICINE COMMUNICATIONS

53. ASSESSMENT. Use ¼ sheet of paper Identification What is the color of the longest wavelength in visible light wave? Which visible light has the highest frequency? The longer the wavelength, the ________ frequency. Essay. Briefly describe the following: Color vs Intensity vs Brightness Sources of light and give 1 example for each.

54. 13 COLORED BLINDNESS

55. 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.

56. Color Blindness Cones Blue Cone Green Cone Red Cone

57. Color Blindness Different types of Color Blindness. Dichromacy The absence of one cone. Protanopia – absence of red sensitive pigment cone (red-blind) Deuteranopia – absence of green sensitive pigment cone (green-blind) Tritanopia – absence of blue sensitive cone (blue-blind)

58. Color Blindness Different types of Color Blindness. Anomalous Trichromacy A deficiency in one of the pigments. Protanomaly – red weakness Deuteranomaly – green weakness Tritanomaly – blue weakness Achromatopsia “no color” People with achromatopsia sees only black, white and shades of gray.