Introduction to Illumination Concepts
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Questions and Answers

What is the primary purpose of the chemicals known as 'getters' in light bulbs?

  • To increase the bulb's operating temperature
  • To enhance the brightness of the bulb
  • To capture tungsten vapour and reduce blackening (correct)
  • To prolong the lifespan of the filament
  • What is one of the main advantages of halogen lamps over traditional incandescent lamps?

  • Higher luminosity with no blackening (correct)
  • They produce colored light
  • They consume less power
  • Lower operating temperature
  • Why are vacuum-type lamps recommended for low wattage applications (up to 40 watts)?

  • They are cheaper to produce
  • They have a longer lifespan than halogen lamps
  • Heat loss from gas introduction exceeds efficiency (correct)
  • They produce brighter light outputs
  • What is a characteristic of gaseous discharge lamps?

    <p>They possess a negative resistance characteristic</p> Signup and view all the answers

    What limits the current in a gaseous discharge lamp to a safe value?

    <p>A choke or ballast</p> Signup and view all the answers

    What is the luminous efficiency range of halogen lamps?

    <p>22 to 33 lumens per watt</p> Signup and view all the answers

    Which of the following gases is NOT commonly used in the manufacturing of gaseous discharge lamps?

    <p>Carbon Dioxide</p> Signup and view all the answers

    What is a notable drawback of traditional incandescent lamps?

    <p>Low efficiency and colored light</p> Signup and view all the answers

    What does the reflection factor measure?

    <p>The proportion of light reflected to the incident light</p> Signup and view all the answers

    How is solid angle denoted and expressed?

    <p>Denoted by 𝜔 and measured in steradians</p> Signup and view all the answers

    According to the law of inverse squares, how does illumination change with distance?

    <p>Illumination decreases inversely with the square of the distance</p> Signup and view all the answers

    What is the purpose of expressing solid angle in steradians?

    <p>To correlate area with angle in a spherical shape</p> Signup and view all the answers

    If the radius of a hollow sphere increases, what happens to the illumination per square mm on its inner surface?

    <p>It decreases inversely to the square of the radius</p> Signup and view all the answers

    How does luminous efficiency change with voltage?

    <p>It is directly proportional to the square of the voltage.</p> Signup and view all the answers

    What is the relationship between filament life and voltage for gas filled lamps?

    <p>Life is inversely proportional to voltage raised to the power of 14.</p> Signup and view all the answers

    Which scenario correctly illustrates the law of inverse squares?

    <p>Illumination on a surface quadrupling with halved distance</p> Signup and view all the answers

    What characteristic makes an angle a solid angle?

    <p>It spans a surface on a sphere</p> Signup and view all the answers

    What is one advantage of using gas filled lamps?

    <p>Direct operation on standard distribution voltage.</p> Signup and view all the answers

    What is the typical diameter of a tungsten lamp filament?

    <p>10 microns.</p> Signup and view all the answers

    Which of the following is true about light emitted by a source in a spherical arrangement?

    <p>Every point on the inner surface receives the same amount of light</p> Signup and view all the answers

    Why is nitrogen added to the gas filled lamps?

    <p>To reduce the possibility of arcing.</p> Signup and view all the answers

    What is the effect of surrounding air temperatures on certain types of lamps?

    <p>It has no effect on operation.</p> Signup and view all the answers

    What happens to a metal filament in an evacuated bulb at temperatures above 2000 ℃?

    <p>It vaporizes quickly and blackens the lamp.</p> Signup and view all the answers

    In the context of filament power dynamics, what is the relationship between absorbed power and radiated power?

    <p>Power absorbed equals power radiated.</p> Signup and view all the answers

    What is the main reason sodium vapour lamps require choke control?

    <p>They are only suitable for alternating current.</p> Signup and view all the answers

    What is the typical power factor of an uncorrected sodium vapour lamp?

    <p>0.3</p> Signup and view all the answers

    How long does it take for a sodium vapour lamp to reach its rated light output?

    <p>15 minutes</p> Signup and view all the answers

    Which color light does a high pressure mercury vapour discharge lamp primarily emit?

    <p>Greenish blue</p> Signup and view all the answers

    What is the main purpose of the outer bulb in a high pressure mercury vapour discharge lamp?

    <p>To absorb harmful ultraviolet rays.</p> Signup and view all the answers

    What is the average efficiency of a sodium vapour lamp under practical conditions?

    <p>40-50 lumens/watt</p> Signup and view all the answers

    What type of gas is present in the inner bulb of a high pressure mercury vapour lamp?

    <p>Argon</p> Signup and view all the answers

    Which component is connected to improve the power factor in a sodium vapour lamp circuit?

    <p>Capacitor</p> Signup and view all the answers

    Which lighting scheme is characterized by more than 90 percent of light flux falling directly on the working plane?

    <p>Direct lighting</p> Signup and view all the answers

    What is the main advantage of using semi-direct lighting in rooms with high ceilings?

    <p>It provides a high level of uniformly distributed illumination.</p> Signup and view all the answers

    In semi-indirect lighting, what percentage of light flux is thrown upwards for diffuse reflection?

    <p>60 to 90%</p> Signup and view all the answers

    Which lighting type is described as having the ceiling act as the light source?

    <p>Indirect lighting</p> Signup and view all the answers

    What unique feature does indirect lighting provide compared to direct lighting?

    <p>Softer and more diffused illumination</p> Signup and view all the answers

    What type of lighting scheme primarily comprises lamps made of diffusing glass?

    <p>General lighting</p> Signup and view all the answers

    What is the primary purpose of using diffusing globes in semi-direct lighting?

    <p>To improve brightness toward the eye</p> Signup and view all the answers

    Which type of lighting scheme is ideal for decorative purposes in theatres or hotels?

    <p>Indirect lighting</p> Signup and view all the answers

    What is the main advantage of using electronic ballasts in CFLs?

    <p>They stabilize lamp current across varying input voltages.</p> Signup and view all the answers

    How does the luminous efficiency of CFLs compare to that of incandescent lamps?

    <p>CFLs have a higher luminous efficiency.</p> Signup and view all the answers

    What is the estimated lifespan of a typical CFL compared to an incandescent lamp?

    <p>CFL lasts about 10 times as long as incandescent.</p> Signup and view all the answers

    What happens to the lifespan of a CFL if it is frequently turned ON and OFF?

    <p>It is significantly reduced.</p> Signup and view all the answers

    What is a drawback of CFLs in terms of energy consumption during manufacturing?

    <p>They consume more energy during manufacturing compared to incandescent lamps.</p> Signup and view all the answers

    What is the typical turn-on time for CFLs compared to incandescent lamps?

    <p>CFLs turn on within a second, but may take time to reach full brightness.</p> Signup and view all the answers

    How do the purchase prices of CFLs compare to those of incandescent lamps?

    <p>CFLs are more expensive but offer long-term savings.</p> Signup and view all the answers

    What factor primarily affects the embodied energy of CFLs when compared to incandescent lamps?

    <p>Manufacturing complexity</p> Signup and view all the answers

    Study Notes

    Introduction to Illumination

    • Artificial lighting advantages: cleanliness, ease of control, reliability, steady output, low cost, and aesthetics.
    • Artificial lighting significance: increased production, reduced worker fatigue, improved eye health and safety, and reduced accidents.
    • Light is radiant energy.
    • Light emitted by hot bodies depends on their temperature.
    • Visible light wavelengths are between 4000 Å and 7500 Å.

    Illumination Concepts

    • Illumination differs from light; light is the cause, illumination is the effect on a surface.
    • Light is radiant energy producing visual sensation (measured in lumen-hours).
    • Luminous flux (F) is total emitted light per second (measured in lumens).
    • Luminous intensity (I) is light flux per unit solid angle (measured in candela).
    • Lumen is the unit of luminous flux (defined as the amount of luminous flux given out).
    • Candle power (CP) is the light radiating capacity of a source (defined as lumens/solid angle).
    • Illumination (E) is lumens per square metre (measured in lux or metre-candle).
    • 1 foot-candle = 1 lumen/ft² = 10.76 metre-candle or lux

    Important Terms

    • Mean horizontal candle power (MHCP): The average of candle powers in horizontal directions.
    • Mean spherical candle power (MSCP): The average of candle powers in all directions.
    • Reduction factor: Ratio of MSCP to MHCP.
    • Lamp efficiency: Ratio of luminous flux to power input (lumens per watt).
    • Specific Consumption: Ratio of the power input to the average candle power (watts per candela).
    • Brightness/Luminance (L): Luminous intensity per unit projected on a surface (candela/m²).
    • Glare: Brightness in field of vision causing eye discomfort, interference with vision or eye fatigue.
    • Space-height ratio: Ratio of horizontal distance between lights and their height.
    • Utilization factor: Ratio of lumens reaching a working plane to lumens from the lamps.
    • Maintenance factor: Ratio of maintained illumination to new illumination.

    Laws of Illumination

    • Inverse Square Law: Illumination is inversely proportional to the square of the distance from the light source.
    • Lambert's Cosine Law: Illumination on a surface is proportional to the cosine of the angle between the light ray and a normal to the surface.

    Illumination at Points Below Light Sources

    • Illumination at a point beneath a light source is the illumination directly below multiplied by the cosine cubed of the angle between the light ray and the normal to the surface at the point being measured.

    Examples and Calculations

    • Worked examples demonstrating calculations of illumination at points on a plane beneath or between lights, showing calculation steps and results.

    Types of Lamps

    • Arc Lamps: Electric discharge through air (carbon-arc, flame-arc, magnetic-arc).
    • High-Temperature Lamps: Oil and gas lamps, incandescent filament lamps.
    • Gaseous Discharge Lamps: Sodium vapor, mercury vapor lamps, fluorescent lamps.
    • Incandescent Lamps: Filament type (tungsten filament)
    • Flame-arc Lamps: Using fluoride-containing materials, generating a high-luminous arc with high efficiency.
    • Fluorescent Tubes: Using a fluorescent coating to convert UV light into visible light (high efficiency, but high initial cost and difficult starting).
    • Halogen Lamps: Tungsten filament lamps filled with halogen gases to prevent filament evaporation (improved efficiency and reduced blackening).

    Comparison of Lamp Types

    • Comparison of tungsten filament and fluorescent lamps highlighting their voltage fluctuations, luminous efficiency, colour characteristics, heat emissions, brightness, lifetime, and maintenance costs. The advantages of each type for various applications are presented.

    Classification of Lighting and Illumination Levels

    • Illumination levels required for different locations in a building (e.g., hallways, living rooms, bedrooms, bathrooms).
    • Illumination levels based on road traffic classification (Group A1, A2, B1, and B2).

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    Illumination PDF

    Description

    This quiz covers essential concepts of illumination and artificial lighting. Explore the significance of various lighting forms, their impact on productivity and safety, and key measurements such as luminous flux and intensity. Test your knowledge on how light affects our working environment.

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