Dispersion of Light and Colours | Jamb(UTME)

Dispersion of White Light by a Triangular Prism

1. Dispersion is the splitting of white light into its component colors when it passes through a prism.
2. A triangular prism bends light because it refracts light at both surfaces.
3. Different colors of light bend by different amounts because each has a different wavelength.
4. Red light bends the least because it has the longest wavelength.
5. Violet light bends the most because it has the shortest wavelength.
6. The spread of colors forms a spectrum, often referred to as the "rainbow effect."
7. The order of colors in the spectrum is red, orange, yellow, green, blue, indigo, violet (ROYGBIV).
8. Dispersion occurs because the refractive index of the prism varies for different wavelengths.
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Production of a Pure Spectrum

9. A pure spectrum is one where the colors are clearly separated without overlapping.
10. To produce a pure spectrum, a narrow beam of white light is passed through a prism.
11. The light must pass through a slit before hitting the prism to reduce overlap.
12. A lens can be used after the prism to focus the spectrum for clarity.
13. A pure spectrum is used in spectrometers to analyze light sources.
14. Pure spectra are important in studying the chemical composition of stars using their light.
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Color Mixing by Addition

15. Color mixing by addition combines primary light colors to produce other colors.
16. The three primary colors of light are red, green, and blue (RGB).
17. Mixing red and green light produces yellow.
18. Mixing red and blue light produces magenta.
19. Mixing blue and green light produces cyan.
20. Combining all three primary colors produces white light.
21. Color addition is used in screens, TVs, and stage lighting.
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Color Mixing by Subtraction

22. Color mixing by subtraction removes certain wavelengths from white light.
23. The primary colors of pigments are cyan, magenta, and yellow (CMY).
24. Mixing cyan and magenta pigments produces blue.
25. Mixing magenta and yellow pigments produces red.
26. Mixing cyan and yellow pigments produces green.
27. Combining all three pigments absorbs all colors, producing black.
28. Subtractive mixing is used in printing and painting.
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Color of Objects

29. The color of an object depends on the light it reflects and absorbs.
30. A red object appears red because it reflects red light and absorbs other colors.
31. A white object reflects all colors of light, while a black object absorbs all colors.
32. Transparent objects, like colored glass, transmit certain colors and absorb others.
33. The perceived color of an object can change under different light sources (e.g., sunlight vs. fluorescent light).
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Color Filters

34. Color filters are materials that allow only certain colors of light to pass through.
35. A red filter transmits red light and absorbs all other colors.
36. A green filter transmits green light while blocking other wavelengths.
37. Filters are used in photography, stage lighting, and optical experiments.
38. Combining different filters demonstrates subtractive color mixing.
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Rainbow and Its Formation

39. A rainbow is a natural spectrum of colors caused by dispersion, reflection, and refraction of light in water droplets.
40. Sunlight enters a raindrop, refracts, and splits into its component colors.
41. The light reflects off the inner surface of the raindrop and exits, creating the rainbow.
42. The primary rainbow is brightest and shows colors in the order of ROYGBIV.
43. A secondary rainbow can sometimes form outside the primary one, with the color order reversed.
44. Rainbows are circular, but the ground usually blocks the bottom half.
45. Rainbows are always seen opposite the Sun, with the observer at the center of the arc.
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Electromagnetic Spectrum

46. The electromagnetic spectrum is a range of all types of electromagnetic radiation, ordered by wavelength and frequency.
47. It includes, from longest to shortest wavelength: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
48. Only the visible spectrum (ROYGBIV) can be seen by the human eye.
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Sources and Uses of Electromagnetic Radiation

Radio Waves

49. Sources: Radio transmitters, stars, and pulsars.
50. Uses: Communication (radio, TV, mobile phones), navigation (GPS), and astronomy.
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Microwaves

51. Sources: Microwave ovens, radar equipment, and cosmic microwave background radiation.
52. Uses: Cooking, radar systems, and satellite communication.
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Infrared

53. Sources: Heat lamps, the Sun, and remote controls.
54. Uses: Night vision, thermal imaging, and remote sensing.
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Visible Light

55. Sources: The Sun, light bulbs, and lasers.
56. Uses: Vision, photography, and illumination.
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Ultraviolet

57. Sources: The Sun, UV lamps, and certain stars.
58. Uses: Sterilization, detecting counterfeit notes, and tanning beds.
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X-rays

59. Sources: X-ray machines, stars, and black holes.
60. Uses: Medical imaging, airport security scans, and studying atomic structures.

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