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Questions and Answers
What is the unit of luminous flux?
What is the unit of luminous flux?
Electromagnetic waves require a medium to travel.
Electromagnetic waves require a medium to travel.
False
What is luminous efficacy?
What is luminous efficacy?
Luminous efficacy is a measure of the luminous flux produced by a light source relative to the power consumed.
The bending of light rays as they pass from one medium to another is called _______________.
The bending of light rays as they pass from one medium to another is called _______________.
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What is the term for the splitting of a ray of white light into its constituent colors?
What is the term for the splitting of a ray of white light into its constituent colors?
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Glare occurs when object luminance exceeds background luminance.
Glare occurs when object luminance exceeds background luminance.
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What is the unit of luminous intensity relative to the light emitted by a candle?
What is the unit of luminous intensity relative to the light emitted by a candle?
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The modification in the intensity of light due to the redistribution of light energy in the region of superposition of two or more light waves is called _______________.
The modification in the intensity of light due to the redistribution of light energy in the region of superposition of two or more light waves is called _______________.
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Match the following units of measurement with their definitions:
Match the following units of measurement with their definitions:
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Study Notes
Electromagnetic Wave and Light
- Electromagnetic waves are formed when an electric field couples with a magnetic field.
- Light is a form of energy that allows us to see.
- Electromagnetic waves do not need a medium to travel.
Dispersion and Light Properties
- Dispersion is the splitting of a ray of white light into its constituent colors.
- Transmittance is the ratio of the total emitted light to the total incident light.
- Reflectance is the ratio of reflected light to incident light.
- Light can be reflected in two ways:
- Specular reflection: on smooth surfaces.
- Diffuse reflection: on rough surfaces.
Light Sources
- There are two main types of light sources:
- Daylight.
- Artificial light, which includes:
- Incandescent lamps.
- Gaseous discharge lamps.
- Electroluminescent lamps.
Luminous Efficacy and Measurement Units
- Luminous efficacy relates the luminous flux produced by a light source to the actual luminous flux emitted.
- Luminous efficacy (lm/W) = Luminous flux (lm) / Power consumed (W).
- Measurement units:
- Lumen (lm): unit of luminous flux, measuring the amount of visible light detectable by the human eye.
- Candela (cd): unit of luminous intensity, relative to the light emitted by a candle.
- Footcandle (fc): unit of illuminance, measuring light intensity on 1 square foot.
- Footlambert: unit of luminance, equal to the luminance of a perfectly diffusing surface that emits or reflects 1 lumen per square foot.
- Lux (lx): unit of illuminance, measuring light intensity on 1 square meter.
- Nits: unit of luminance, equal to the luminance of a perfectly diffusing surface that emits or reflects 1 candle per square meter.
Light Behavior and Interference
- Refraction: bending of light rays as they pass from one medium to another, changing the path of the rays.
- Diffraction: slight bending of light as it passes around the edge of an object.
- Interference: modification in light intensity due to redistribution of light energy in the region of superposition of two or more light waves.
- Glare: occurs when background luminance exceeds object luminance.
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Description
Learn about the characteristics of electromagnetic waves, light, and its properties, including dispersion, transmittance, and reflectance. Explore different light sources, including daylight and artificial light.
