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Questions and Answers
What is the primary purpose of the chemicals known as 'getters' in light bulbs?
What is the primary purpose of the chemicals known as 'getters' in light bulbs?
What is one of the main advantages of halogen lamps over traditional incandescent lamps?
What is one of the main advantages of halogen lamps over traditional incandescent lamps?
Why are vacuum-type lamps recommended for low wattage applications (up to 40 watts)?
Why are vacuum-type lamps recommended for low wattage applications (up to 40 watts)?
What is a characteristic of gaseous discharge lamps?
What is a characteristic of gaseous discharge lamps?
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What limits the current in a gaseous discharge lamp to a safe value?
What limits the current in a gaseous discharge lamp to a safe value?
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What is the luminous efficiency range of halogen lamps?
What is the luminous efficiency range of halogen lamps?
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Which of the following gases is NOT commonly used in the manufacturing of gaseous discharge lamps?
Which of the following gases is NOT commonly used in the manufacturing of gaseous discharge lamps?
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What is a notable drawback of traditional incandescent lamps?
What is a notable drawback of traditional incandescent lamps?
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What does the reflection factor measure?
What does the reflection factor measure?
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How is solid angle denoted and expressed?
How is solid angle denoted and expressed?
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According to the law of inverse squares, how does illumination change with distance?
According to the law of inverse squares, how does illumination change with distance?
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What is the purpose of expressing solid angle in steradians?
What is the purpose of expressing solid angle in steradians?
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If the radius of a hollow sphere increases, what happens to the illumination per square mm on its inner surface?
If the radius of a hollow sphere increases, what happens to the illumination per square mm on its inner surface?
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How does luminous efficiency change with voltage?
How does luminous efficiency change with voltage?
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What is the relationship between filament life and voltage for gas filled lamps?
What is the relationship between filament life and voltage for gas filled lamps?
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Which scenario correctly illustrates the law of inverse squares?
Which scenario correctly illustrates the law of inverse squares?
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What characteristic makes an angle a solid angle?
What characteristic makes an angle a solid angle?
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What is one advantage of using gas filled lamps?
What is one advantage of using gas filled lamps?
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What is the typical diameter of a tungsten lamp filament?
What is the typical diameter of a tungsten lamp filament?
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Which of the following is true about light emitted by a source in a spherical arrangement?
Which of the following is true about light emitted by a source in a spherical arrangement?
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Why is nitrogen added to the gas filled lamps?
Why is nitrogen added to the gas filled lamps?
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What is the effect of surrounding air temperatures on certain types of lamps?
What is the effect of surrounding air temperatures on certain types of lamps?
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What happens to a metal filament in an evacuated bulb at temperatures above 2000 ℃?
What happens to a metal filament in an evacuated bulb at temperatures above 2000 ℃?
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In the context of filament power dynamics, what is the relationship between absorbed power and radiated power?
In the context of filament power dynamics, what is the relationship between absorbed power and radiated power?
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What is the main reason sodium vapour lamps require choke control?
What is the main reason sodium vapour lamps require choke control?
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What is the typical power factor of an uncorrected sodium vapour lamp?
What is the typical power factor of an uncorrected sodium vapour lamp?
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How long does it take for a sodium vapour lamp to reach its rated light output?
How long does it take for a sodium vapour lamp to reach its rated light output?
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Which color light does a high pressure mercury vapour discharge lamp primarily emit?
Which color light does a high pressure mercury vapour discharge lamp primarily emit?
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What is the main purpose of the outer bulb in a high pressure mercury vapour discharge lamp?
What is the main purpose of the outer bulb in a high pressure mercury vapour discharge lamp?
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What is the average efficiency of a sodium vapour lamp under practical conditions?
What is the average efficiency of a sodium vapour lamp under practical conditions?
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What type of gas is present in the inner bulb of a high pressure mercury vapour lamp?
What type of gas is present in the inner bulb of a high pressure mercury vapour lamp?
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Which component is connected to improve the power factor in a sodium vapour lamp circuit?
Which component is connected to improve the power factor in a sodium vapour lamp circuit?
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Which lighting scheme is characterized by more than 90 percent of light flux falling directly on the working plane?
Which lighting scheme is characterized by more than 90 percent of light flux falling directly on the working plane?
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What is the main advantage of using semi-direct lighting in rooms with high ceilings?
What is the main advantage of using semi-direct lighting in rooms with high ceilings?
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In semi-indirect lighting, what percentage of light flux is thrown upwards for diffuse reflection?
In semi-indirect lighting, what percentage of light flux is thrown upwards for diffuse reflection?
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Which lighting type is described as having the ceiling act as the light source?
Which lighting type is described as having the ceiling act as the light source?
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What unique feature does indirect lighting provide compared to direct lighting?
What unique feature does indirect lighting provide compared to direct lighting?
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What type of lighting scheme primarily comprises lamps made of diffusing glass?
What type of lighting scheme primarily comprises lamps made of diffusing glass?
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What is the primary purpose of using diffusing globes in semi-direct lighting?
What is the primary purpose of using diffusing globes in semi-direct lighting?
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Which type of lighting scheme is ideal for decorative purposes in theatres or hotels?
Which type of lighting scheme is ideal for decorative purposes in theatres or hotels?
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What is the main advantage of using electronic ballasts in CFLs?
What is the main advantage of using electronic ballasts in CFLs?
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How does the luminous efficiency of CFLs compare to that of incandescent lamps?
How does the luminous efficiency of CFLs compare to that of incandescent lamps?
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What is the estimated lifespan of a typical CFL compared to an incandescent lamp?
What is the estimated lifespan of a typical CFL compared to an incandescent lamp?
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What happens to the lifespan of a CFL if it is frequently turned ON and OFF?
What happens to the lifespan of a CFL if it is frequently turned ON and OFF?
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What is a drawback of CFLs in terms of energy consumption during manufacturing?
What is a drawback of CFLs in terms of energy consumption during manufacturing?
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What is the typical turn-on time for CFLs compared to incandescent lamps?
What is the typical turn-on time for CFLs compared to incandescent lamps?
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How do the purchase prices of CFLs compare to those of incandescent lamps?
How do the purchase prices of CFLs compare to those of incandescent lamps?
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What factor primarily affects the embodied energy of CFLs when compared to incandescent lamps?
What factor primarily affects the embodied energy of CFLs when compared to incandescent lamps?
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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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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.