Illumination MCQ Quiz in मल्याळम - Objective Question with Answer for Illumination - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

Discharge Lamps:

• In all discharge lamps, an electric current is passed through a gas or vapor which renders it luminous.
• The elements most commonly used in this process of producing light by gaseous conduction are neon, mercury, and sodium vapors.
• The colors (i.e. wavelength) of light produced depend on the nature of the gas or vapor.
• For example, the neon discharge yields orange-red light of nearly 6,500 A.U. which is very popular for advertising signs and other spectacular effects.
• The pressure used in neon tubes is usually from 3 to 20 mm of Hg.
• High-pressure mercury vapor lamps, Neon lamps, Sodium vapor lamps, etc are examples of discharge-type lamps.
• Mercury-vapour light is always bluish-green and deficient in red rays, whereas sodium vapor light is orange-yellow.
• The discharge lamps work on the discharge phenomenon i.e, the voltage needs to discharge the ion from one side of the electrode to another side due to this high voltage is needed to pass the ion than the current so the current will lag behind the voltage at the normal working time.
• Hence Discharge lamp working at a lagging power factor.
• Due to the addition of the Choke and Capacitor, it has a high initial cost.
• It required approximately 5 minutes for starting due to the ionization process phenomena.

Lighting Schemes:
Different lighting schemes may be classified as,
(i) Direct lighting scheme
(ii) Indirect lighting scheme
(iii) Semi-direct lighting scheme
(iv) Semi-indirect lighting scheme
(v) General diffusing scheme

(i) Direct Lighting Scheme:

• It is the most commonly used type of lighting scheme.
• In this scheme, more than 90% of the total light flux is made to fall directly on the working plane with the help of a suitable deep reflector.
• It is the most efficient but causes hard shadow and glare.
• The utilization factor of indirect lighting systems is about 40% to 60%.
• It is mainly used for industrial and general outdoor lighting.
   

(ii) Indirect Lighting Scheme:

• In this system, more than 90% of the total light flux is thrown upward to the ceiling for diffuse reflection by using inverted or bowl reflectors.
• In such a system ceiling act as a light source, and the glare is reduced to a minimum.
• The resulting illumination in that system is softer and more diffuser, and less shadow prominent.
• The utilization factor in an indirect lighting system is about 10% to 35%.
• It is used for decoration purposes in cinemas, theaters, and hotels, and in workshops where large machines and other obstructions would cause troubleshooting shadows if direct lighting is applied.
   

(iii) Semi-Direct Lighting Scheme:

• In this lighting scheme, 60 to 90% of total light flux is made to fall downwards directly with the help of semi-direct reflectors, and the remaining light is used to illuminate the ceiling and walls.
• This system is widely used for a room with a high ceiling where a high level of uniformly distributed illumination is required.
   

(iv) Semi-Indirect Lighting Scheme:

• In this lighting scheme, 60 to 90% of total light flux is thrown upward to the ceiling for diffuse reflection and the rest reaches the working plane directly except for some absorption by the bowl.
• It is mainly used for indoor lighting decoration purposes.
   

(v) General Diffusing Scheme:

• In this system, luminaries are employed which have almost equal light distribution downwards and upwards.
   

General Classification of Luminaries:

The correct answer is option 4): (Automobile light)

Concept:

Evolution of automobile lighting:

• In earlier days incandescent lamps of  6V,12 V, and 24 V are used in automobile lighting
• Then halogen lamps are used for automotive lighting. Which has twice the light output, higher color temperature, and double service life than incandescent lamps
•  Nowadays low voltage LED lamps are being used for automotive lighting.
• Insensitive to the number of switching operations, Low energy consumption and Low temperature are characteristics of LED lamp which supports common usage of automobile lighting

Additional Information

The correct answer is option 3
Concept:
Direct Lighting:

• In this lighting scheme, more than 90 percent of the total light flux is made to fall directly on the working plane with the help of deep reflectors.
• This scheme is the most efficient but causes hard shadows and glare.
• It is mainly used for industrial and general outdoor lighting.

Semi-direct lighting:

• In this lighting scheme, 60 to 90 percent of the total light flux is made to fall downwards directly with the help of semi-direct reflectors, remaining light is used to illuminate the ceiling and walls.
• It is best suited to rooms with high ceilings where a high level of uniformly distributed illumination is desirable like offices and specific objectives.
• Glare in such units is avoided by employing diffusing globed which not only improves the brightness towards the eye but improves the efficiency of the systems with reference to the working place.

Indirect lighting:

• In this light scheme, more than 90 percent of total light flux is thrown upwards to the ceiling for diffuse re­flection by using inverted or bowl reflectors.
• In this scheme, the ceiling acts as the lighting source, and glare is reduced to a minimum.
• It produces shadowless illumination, which is very useful for drawing offices and in workshops where large machines and other difficulties would cause troublesome shadows if direct lighting schemes were used.

Semi-indirect lighting:

• In this lighting scheme, 60 to 90 percent of total light flux is thrown upwards to the ceiling for diffuse reflection and the rest reaches the working plane directly.
• In this scheme, lighting will be completely eliminated.
• It is mainly used for indoor light decoration purposes.

• Illuminance - It is the measurement of the amount of light falling on a defined surface area.
• The formula is the luminous flux per unit area.
• Luminous Flux - It is the measurement of the total amount of visible light emitted by a light source.
• Lumen is the SI unit of luminous flux.
• Watt is the unit of Power and Joule is the unit of work or energy.

CONCEPT:

Law of illumination:

Law of inverse squares:

According to the Law of inverse squares, illumination of a surface is inversely proportional to the square of the distance between the surface and the light source.

\(E = \frac{I}{{{d^2}}}\)

Where E is the illuminance

I is the luminous intensity

D is the distance between the surface and the source

Lambert's cosine law:
This law states that ‘illumination, E at any point on a surface is directly proportional to the cosine of the angle between the normal at that point and the line of flux.

\(E = \frac{Icos\theta}{{{d^2}}}\)

Types of electric lamps:

1.) Discharge lamp:

• An electric discharge lamp is a family of artificial light sources that generate light by sending an electric discharge between two electrodes in a gas or vapor.
• The most commonly used elements in these types of lamps are neon, mercury, and sodium vapors.

2.) Metal arc lamp:

• A metal arc lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides.
• Metal arc lamps have a high luminous efficacy of about twice that of mercury vapor lights and 3 to 5 times that of incandescent lights and produce intense white light.

3.) Halogen bulb:

• The halogen lamp is a type of incandescent lamp that uses a halogen gas in order to produce light.
• In a typical incandescent lamp, tungsten slowly evaporates from the burning filament. This causes the blackening of the lamp, which decreases light output and reduces life. 
• Halogen lamps are largely able to eliminate this problem because the halogen gas reacts chemically with the evaporated tungsten to prevent it from affixing to the glass.

4.) Vacuum lamp:

• A vacuum lamp controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
• The lamps use thermionic emission of electrons from a hot cathode for producing light.

Concept:

Light and Fan sub-circuits:

• There are maximum 10 points in light and fan sub-circuit as per IE (Indian Electricity) rules.
• The maximum load for a single light and fan sub-circuit should not exceed 800 W.

Power sub-circuit:

• The maximum load for power sub-circuit should not exceed 3000 W
• The number of outlets restricted to two in each power subcircuit.
• If the power load exceeds above 3000 W, a separate power circuit is taken

The stroboscopic effect in fluorescent lamp is a phenomenon which causes running or moving equipment to appear stationary or appear to be operating slower than they actually are.

Fluorescent lamps are provided with 50 Hz ac current supply. When operating under this frequency the lamp becomes zero (crosses zero wave) double the supply frequency, i.e, 100 times for 50 Hz frequency per second. Due to the persistence of vision our eyes do not notice those flickering.

However if the light falls on the moving parts due to illusion, they may appear to be either running slow, or in reverse direction or even may appear stationary. This effect is called stroboscopic effect.

This can be prevented by connecting the twin-tube lights in parallel.

Each tube uses a separate choke and a separate starter, and a capacitor is added in series with the second choke, so as to improve the capacitor. We can also avoid the flickering of tube lights.

1.) Light intensity

The light intensity or luminous intensity is the amount of light that falls on a surface across a certain square foot or square meter.

The intensity of light is measured in lumens per square meter (lux) or Candela.

2.) Luminous flux

The luminous flux or luminous power is the measure of the perceived power of light.

It is measured in Lumen.

3.) Luminance

Luminance is the intensity of light emitted from a surface per unit area in a given direction.

It is measured in Lux.

4.) Illuminance

It is the total luminous flux incident on a surface, per unit area. 

It is measured in lumens/m².