Which among the below set of colours are generally known as the primary colours of light?

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NTPC CBT 2 2016 Previous Paper 5 (Held On: 18 Jan 2017 Shift 2)
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  1. White, Yellow, Blue
  2. Red, Green, Blue
  3. Red, Green, Black
  4. Black, White, Red

Answer (Detailed Solution Below)

Option 2 : Red, Green, Blue
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Detailed Solution

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The correct answer is Red, Green, Blue.

  • Red, green, and blue are the primary colours of light—they can be combined in different proportions to make all other colors.
  • There are two colour models:
    • Light Color Primaries (Red, Green, Blue).
    • Pigment Color Primaries (Cyan, Magenta, Yellow).

Important Points

  • Primary colours make all other colours:
    • Red + Green = Yellow.
    • Green + Blue = Cyan.
    • Blue + Red = Magenta.
  • There are three Secondary Colors (S'): Orange, Green, Violet.
  • There are six Tertiary Colors (Ts): Red-Orange, Yellow-Orange, Yellow-Green, Blue-Green, Blue-Violet, Red-Violet.
    • Tertiary is formed by mixing a primary with a secondary.

Additional Information

  • In terms of wavelengths, visible light ranges from about 400 nm to 700 nm.
  • light with a wavelength of about 400 nm is seen as violet, and light with a wavelength of about 700 nm is seen as red.

Key Points

  • The inner surfaces of human eyes contain photoreceptors—specialized cells that are sensitive to light and relay messages to the brain.
    • There are two types of photoreceptors: cones (which are sensitive to colour) and rods (which are more sensitive to intensity).
    • Humans are able to see an object when light from the object and enters their eyes and strikes these photoreceptors.
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