High-pressure mercury- vapour lamp emits:

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ALP CBT 2 Electrician Previous Paper: Held on 22 Jan 2019 Shift 3
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  1. Red colour light
  2. Yellow colour light
  3. White colour light
  4. Bluish White colour light

Answer (Detailed Solution Below)

Option 4 : Bluish White colour light
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  • Generally high-pressure mercury- vapor lamp emits greenish-blue light. But from the options most probable answer is bluish-white color light.
  • The mercury vapor lamp is a high-intensity discharge lamp. It uses an arc through vaporized mercury in a high-pressure tube to create very bright light directly from its own arc.
  • Mercury vapor lamp is deficient in red light.
  • It emits a characteristic greenish-blue light.
  • It produces color distortion.
  • It has an efficiency of about 40 lumens per watt.

  • Important:

    Advantages:

    • Good efficiency
    • Color rendering is better than that of high-pressure sodium street lights
    • Some lamps last far longer than the 24000-hour mark, sometimes 40 years


    Disadvantages:

    • Like many lamps, it contains traces of mercury which must be disposed of properly
    • Human skin looks green under the light, it is poor for color film/photography
    • The warm-up time required to start the lamp


    Applications:

    • Large areas like parks, street lighting, high ceiling buildings, and gyms.
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