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Illumination

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The radiant efficiency of the luminous source depends on

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  • The radiant efficiency of a luminous source is dependent on the temperature of the source.
  • The temperature of the source determines the amount of energy that is emitted as visible light, which is known as luminous efficacy.
  • The higher the temperature of the source, the more efficient it is at emitting light.
  • This is due to the fact that as the temperature of the source increases, it emits more light per unit of power consumed, resulting in higher radiant efficiency.
  • This is also why sources such as incandescent light bulbs and candle flames are less efficient at converting energy into light than sources such as LED lights or fluorescent bulbs, which operate at cooler temperatures.

Lightwave travel with a velocity of

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  • Lightwave travel with a velocity of 3 × 1010 cm/s.
  • This is often denoted by the symbol "c" in scientific equations and is considered to be a fundamental constant of nature.
  • The speed of light is important in many areas of science and technology, including optics, electromagnetism, and relativity.

Carbon arc lamps are commonly used in

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  • Carbon arc lamps are commonly used in Cinema Projector.
  • The carbon arc lamp consists of two carbon electrodes separated by a small gap.
  • When an electric current is passed through the electrodes, the gap between them becomes a highly ionized plasma, which emits light as it heats up.
  • In early cinema projectors, carbon arc lamps were the primary source of light.
  • Due to their high operating temperatures and relatively short lifespan, they were eventually replaced by other types of lamps such as xenon arc lamps and metal halide lamps.

The unit of solid angle is

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  • The unit of solid angle is Steradian.
  • It is defined as the solid angle subtended at the center of a sphere by a surface that is equal in area to the square of the radius of the sphere.
  • One steradian is equal to the solid angle that is subtended by a part of a sphere's surface that has an area equal to the radius squared.

Candela is the unit of

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  • Candela is the unit of Luminous intensity.
  • It is the amount of light emitted in a particular direction per unit of time by a light source.
  • The candela is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 Hz and has a radiant intensity in that direction of 1/683 watt per steradian.

The unit of luminous flux is

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  • The unit of luminous flux is Lumen.
  • The lumen (lm) is the unit of measurement for luminous flux, which is the amount of visible light emitted by a light source per unit time.
  • The higher the number of lumens emitted by a light source, the brighter it appears to the human eye.

The illumination is directly proportional to the cosine of the angle made by the normal to the illuminated surface with the direction of the incident flux. The above statement is associated with

Discuss
  • The illumination is directly proportional to the cosine of the angle made by the normal to the illuminated surface with the direction of the incident flux. The above statement is associated with Lambert's cosine law.
  • Lambert's cosine law, also known as the cosine emission law or Lambert's law, states that the illumination or brightness of a surface is directly proportional to the cosine of the angle between the normal to the surface and the direction of the incident light.
  • This means that the amount of light falling on a surface decreases as the angle between the surface and the incident light increases.

Illumination level required for precision work is around

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Illumination level required for precision work is around 500 lm/m2.

The intensity of illumination required on a surface can vary depending on the type of work being done, as well as other factors such as the age and visual acuity of the worker, the reflectivity of the surrounding surfaces, and the lighting conditions in the environment.

For normal activities such as reading and writing, light levels in the range of 100-300 lux are typically sufficient.

However, for precision work that requires a high level of visual acuity and attention to detail, such as electronic assembly or medical procedures, light levels of 1500-2000 lux or higher may be required to provide adequate illumination and minimize eye strain and fatigue.

Which of the following will need the highest level of illumination?

Discuss
  • Proofreading will need the highest level of illumination.
  • Proofreading is a precision task that requires a high level of visual acuity and attention to detail.
  • In order to perform this task accurately and efficiently, it is important to have a well-lit environment with adequate illumination.
  • For precision work that requires a high level of visual acuity and attention to detail, light levels of 1500-2000 lux or higher may be required to provide adequate illumination and minimize eye strain and fatigue.

 

Which of the following will need the lowest level of illumination?

Discuss
  • Railway platform will need the lowest level of illumination.
  • The recommended illumination level for a railway platform is between 50-100 lux, which is lower than the recommended illumination levels for other activities such as office work, laboratories, or detailed mechanical work.
  • This is because the visual tasks on a railway platform are typically limited to basic orientation and movement, which can be achieved with lower levels of illumination.

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