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Questions and Answers
What happens to charge carriers when a DC power supply is applied to an LED lamp?
What happens to charge carriers when a DC power supply is applied to an LED lamp?
Which semiconductor materials are known to emit light upon the recombination of electrons and holes?
Which semiconductor materials are known to emit light upon the recombination of electrons and holes?
Which of the following is NOT an advantage of LEDs?
Which of the following is NOT an advantage of LEDs?
What is a common application of LEDs?
What is a common application of LEDs?
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What can cause damage to an LED?
What can cause damage to an LED?
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What is the primary purpose of street lighting?
What is the primary purpose of street lighting?
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Which intersections are prioritized for street lighting?
Which intersections are prioritized for street lighting?
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What design principle employs reflectors that spread light uniformly over the road surface?
What design principle employs reflectors that spread light uniformly over the road surface?
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What is the purpose of having a cut-off angle of 30° to 45° in the design of reflectors?
What is the purpose of having a cut-off angle of 30° to 45° in the design of reflectors?
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Which method is commonly used to calculate illumination at a specific point on the road surface?
Which method is commonly used to calculate illumination at a specific point on the road surface?
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How does street lighting affect traffic flow conditions?
How does street lighting affect traffic flow conditions?
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What type of lighting is especially critical at sites such as level crossings and bridge sites?
What type of lighting is especially critical at sites such as level crossings and bridge sites?
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What is NOT a benefit of street lighting?
What is NOT a benefit of street lighting?
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What is the primary disadvantage of using the specular reflection principle for street lighting?
What is the primary disadvantage of using the specular reflection principle for street lighting?
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Which illumination level is required for Class A street lighting installations?
Which illumination level is required for Class A street lighting installations?
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What is the ideal mounting height range for street lamps?
What is the ideal mounting height range for street lamps?
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Which of the following factors is NOT considered when calculating luminance for street lighting?
Which of the following factors is NOT considered when calculating luminance for street lighting?
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Which is a characteristic of sodium vapor lamps?
Which is a characteristic of sodium vapor lamps?
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What spacing distance is recommended for street lamps to ensure adequate visibility?
What spacing distance is recommended for street lamps to ensure adequate visibility?
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What is the role of the choke in a sodium vapor lamp circuit?
What is the role of the choke in a sodium vapor lamp circuit?
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What is the maintenance factor (MF) assumed to be when calculating lamp spacing?
What is the maintenance factor (MF) assumed to be when calculating lamp spacing?
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Why should lamp posts be avoided near large trees?
Why should lamp posts be avoided near large trees?
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What is the primary purpose of a capacitor in a sodium vapor lamp circuit?
What is the primary purpose of a capacitor in a sodium vapor lamp circuit?
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What is the principle by which a tungsten filament lamp produces light?
What is the principle by which a tungsten filament lamp produces light?
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What happens to the glass of a tungsten filament lamp when the filament begins to break up?
What happens to the glass of a tungsten filament lamp when the filament begins to break up?
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What is the impact of operating a tungsten filament lamp at a voltage higher than its rated voltage?
What is the impact of operating a tungsten filament lamp at a voltage higher than its rated voltage?
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Which gas is typically used to fill the bulb of a tungsten filament lamp to reduce filament evaporation?
Which gas is typically used to fill the bulb of a tungsten filament lamp to reduce filament evaporation?
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During the start-up of a mercury vapor lamp, what changes color before the lamp illuminates?
During the start-up of a mercury vapor lamp, what changes color before the lamp illuminates?
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What is a common characteristic of the electrodes in a mercury vapor lamp?
What is a common characteristic of the electrodes in a mercury vapor lamp?
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What is the primary mechanism by which a fluorescent lamp emits visible light?
What is the primary mechanism by which a fluorescent lamp emits visible light?
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What component is responsible for providing high starting voltage in a mercury vapor lamp?
What component is responsible for providing high starting voltage in a mercury vapor lamp?
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How does the presence of a choke affect the operation of a fluorescent lamp after it is started?
How does the presence of a choke affect the operation of a fluorescent lamp after it is started?
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What is the typical rated life of a general lighting service (GLS) filament lamp under normal conditions?
What is the typical rated life of a general lighting service (GLS) filament lamp under normal conditions?
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What is the effect of the momentary high potential difference between the filaments in a lamp?
What is the effect of the momentary high potential difference between the filaments in a lamp?
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Which material is commonly used for the reflecting surfaces in flood lighting?
Which material is commonly used for the reflecting surfaces in flood lighting?
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What factor is significant when calculating the number of projectors required for flood lighting?
What factor is significant when calculating the number of projectors required for flood lighting?
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What is the utilization factor (UF) in lighting design?
What is the utilization factor (UF) in lighting design?
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What is the role of ventilation in flood lighting systems?
What is the role of ventilation in flood lighting systems?
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What does the depreciation factor account for in flood lighting calculations?
What does the depreciation factor account for in flood lighting calculations?
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What type of light source is an LED (Light Emitting Diode)?
What type of light source is an LED (Light Emitting Diode)?
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Which of the following factors does NOT influence the utilization factor (UF)?
Which of the following factors does NOT influence the utilization factor (UF)?
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Which application is NOT typically associated with flood lighting?
Which application is NOT typically associated with flood lighting?
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What causes fluorescence in a phosphor coating within a lamp?
What causes fluorescence in a phosphor coating within a lamp?
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Study Notes
Street Lighting Introduction
- Street lighting is used on the side of roads, medians, and suspended above the road to provide illumination.
- Street lighting is essential for safe, comfortable, and convenient movement of vehicles and pedestrians at night.
- It enhances visibility, decreases driving stress, and improves traffic flow.
Street Lighting Principles
-
Diffusion Principle:
- Lamps are equipped with reflectors that direct light downwards and spread it uniformly across the road surface.
- Reflectors have a cut-off angle to minimize glare.
- Road surface illumination is calculated using the inverse-square law.
-
Specular Reflection Principle:
- Reflectors curve upward to concentrate light at a large angle of incidence.
- This method is suitable for straight road sections.
- It is more economical than the diffusion method, but can produce glare.
Street Lighting Illumination Levels
- Illumination levels depend on the type of street and its use.
- Well-lit streets require 8 to 15 lumens per square meter.
- Luminance, a measure of light reflected from the pavement, is important for visibility.
- Illuminance and luminance levels depend on the light source, luminaire distribution, mounting height, pole spacing, and pavement reflectance.
Street Lamp Mounting Height
- Lamp height and overhang affect light distribution, shadows, and brightness.
- Pole heights range from 6 to 9 meters.
- Overhang provides good light distribution and minimizes glare.
- Lamps should be placed at road junctions and away from large trees.
Street Lamp Spacing
- Closer spacing ensures good brightness and visibility at night.
- Spacing varies depending on the road's importance.
- Spacing should be from 35 to 55 meters for most roads.
Sodium Vapor Lamp
- Generates light through excited sodium atoms.
- Consists of a glass tube containing sodium and argon/neon gas.
- A choke and transformer are used to stabilize the discharge and provide heat.
- Generates yellow light.
- Available in various wattages.
Tungsten Filament Lamp
- Produces light by heating a tungsten filament to high temperatures.
- Works on the principle of incandescence.
- Uses argon/nitrogen gas to reduce evaporation.
- Filament lifespan can be affected by operating voltage.
Mercury Vapor Lamp
- Creates light through an electric arc in mercury vapor.
- Requires high voltage to start the arc.
- Takes several minutes to reach full brightness.
- Uses an ignitor to provide a high starting voltage.
Fluorescent Lamp
- Low-pressure mercury vapor lamp that uses fluorescence.
- Consists of a glass tube coated with phosphor and containing mercury and argon gas.
- Emits visible light through phosphor luminescence.
- Uses a choke and starter switch to activate the arc.
Flood Lighting
- Uses high-intensity projectors to illuminate large surfaces.
- Reflectors direct light into narrow beams.
- Calculations consider illumination level, projector type, and number of projectors.
- Waste light factor accounts for overlapping and light falling beyond the illuminated area.
- Depreciation factor addresses light loss due to surface dirt.
- Coefficient of utilization calculates the ratio of beam lumens to lamp lumens.
Applications of Flood Lighting
- Architectural buildings and monuments
- Ports
- Building facades
- Manufacturing plants
- Construction sites
Utilisation Factor (UF)
- The proportion of light reaching the working plane compared to the lamp's output.
- Influenced by room reflectance, shape, light output ratio, and mounting height.
- The UF is typically expressed as a number less than 1.
LED - Light Emitting Diode
- Converts electrical energy directly into light energy.
- Emits light when current flows through a PN junction.
- Used in various applications, including lighting, displays, and sensors.
Light Emitting Diode (LED)
- LEDs are semiconductor devices that emit light when an electron transitions from a higher energy band to a lower energy band.
- This energy release occurs when an electron and a hole recombine, releasing energy in the form of light or heat.
- Materials like gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), and gallium nitride (GaN) are used in LEDs for their light-emitting properties.
- The emitted light is transferred outside the device if the semiconductor material is translucent.
LED Lamp Function
- When connected to a DC power supply in forward bias, electrons flow towards the positive terminal and holes towards the negative terminal.
- These charge carriers recombine at the PN junction, releasing energy.
- The energy can be released as heat or light, depending on the material.
Advantages of LED
- Lower Cost and Smaller Size: LEDs are more cost-effective and have a compact design than conventional light bulbs.
- Electricity Control: LED brightness can be precisely adjusted using microcontrollers.
- Long Lifespan: LEDs have a significantly longer lifespan than traditional bulbs.
- Energy Efficiency: LEDs convert a higher percentage of electrical energy into light, making them energy-efficient.
- Instant On: LEDs do not have a warm-up period, switching on instantly.
- Durability: LEDs are robust and can withstand harsh environments.
- Cold Temperature Tolerance: LEDs function efficiently in cold temperatures.
- Directional Light: LEDs emit light in a specific direction.
- Excellent Color Rendering: LEDs provide accurate color reproduction.
- Environmentally Friendly: LEDs are mercury-free and recyclable.
- Controllable: LED lighting patterns and brightness can be easily adjusted.
- Small Size and Portability: They are small enough to be stacked together for display applications.
- High Efficiency: LEDs convert power to light energy more efficiently than traditional incandescent bulbs.
Disadvantages of LEDs
- Overvoltage or Overcurrent: Excessive current can permanently damage LEDs.
- Overheating: Excessive radiant power can lead to overheating and potential damage.
Applications of LED
- Lighting: LEDs are widely used in homes, industries, vehicles, and traffic signals.
- Displays: LEDs are used in mobile phones, watches, and display boards.
- Fault Indicators: LEDs are employed as fault indicators in control panels.
- Decorative Lighting: LEDs are commonly used for decorative purposes.
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Description
This quiz covers the fundamental principles and importance of street lighting, including diffusion and specular reflection methods. Learn about how street lighting enhances visibility and safety for vehicles and pedestrians at night. Test your knowledge on the various illumination levels applicable to street lighting.
