100 Most Important MCQ Of Illumination with answer & explanation

Answer.3. Railway platform

Explanation:-

Railway platform, Hospital ward requires a low level of illumination but the amount of illumination also depends on the platform size, structure ( Open, Covered), and the number of passengers.

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Answer.1. Sodium vapor lamp

Explanation:-

Monochrome color schemes have only one color, while adjacent color runs have at least three colors. “Monochrome” is from two Greek words, mono meaning “one” and chrome meaning “color.” A monochrome scheme includes the hue and all of its shades and tints. 

A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.

There are two varieties of such lamps:

1. Low-pressure sodium lamp
2. High-pressure sodium lamp

Both the low pressure and high pressure are filled with both sodium and Neon gas.

Low-pressure sodium lamps are highly efficient electrical light sources, but their yellow light restricts applications to outdoor lighting such as street lamps.

High-pressure sodium lamps produce a broader spectrum of light than low-pressure lamps, but they still have poorer color rendering producing the monochromatic yellow light 

On turning on a sodium vapor lamp, initially, it emits a dim red/ pink light, which warms up sodium metal. After a few minutes, the light turns bright yellow, due to the vaporization of sodium, which is a nearly monochromatic light. Objects, lighted by sodium vapor lamps are not easily distinguished in color, because they appear almost entirely yellow due to the reflection of this narrow bandwidth of yellow light.

Answer.4. 100-140 lumens/m²

Explanation:-

The average illumination of the house is 100-150 lumens/m²

Answer.4. 60-65 lumens/watt

Explanation:-

Compact fluorescent (CFL) 

Compact fluorescent (CFL) lamps are becoming more popular.

1. CFLs are available in a wide spectrum of colors (2700 K is the closest to incandescent
2. CFLs take a few minutes to warm up and produce full intensity.
3. CFLs are cool to the touch.
4. CFL’s can emit 70 – 90 lumens watts.
5. CFLs are high efficiency.
6. CFLs have a long life expectancy (8000 hours).
7. CFLs have a moderate cost.

Answer.1. One lux

Explanation:-

The FOOTCANDLE is the unit of measure of the density of light striking a surface and is measured in lumens of light per square foot of area. One footcandle is, by definition, equal to 1 lumen striking square foot. The foot-candle is the commonly used unit of luminance.

The Sl unit of luminance is the LUX, which is defined as lumens per square meter. One footcandle is approximately 10.76 lux.

Answer.2. 40 Watt

Explanation:-

Fluorescent lamps are much more efficient than incandescent lamps and have up to 20 times longer life than some incandescents. For these reasons, they are widely used instead of incandescent lamps, except for specialty lighting and residential use. For example, more light is emitted by a 40-W fluorescent tube than by a 100-W incandescent bulb. The fluorescent luminaire is more than twice as efficient as the incandescent bulb, even including the electrical losses from the ballast needed to operate fluorescent lamps. The ballast typically consumes an added 15 to 20 percent of the rated wattage of the fluorescent lamp.

The shape of fluorescent lamps is tubular, and most are straight tubes. The standard 4-foot ( 1 .2-m) tube is rated at 40 watts. As an option, energy-conserving reduced-wattage lamps are available to decrease power consumption. 

Wattage comparison between standard and energy-conserving fluorescent tube

Answer.4. GSL Lamp

Explanation:-

GSL Lamp

GLS lamps produce light as a result of the heating effect of an electrical current. Most of the electricity goes to producing heat and a little to producing light. A fine tungsten wire is first coiled and coiled again to form the incandescent filament of the GLS lamp. The coiled-coil arrangement reduces filament cooling and increases the light output by allowing the filament to operate at a higher temperature. The light output covers the visible spectrum, giving a warm white to yellow light with a color rendering quality classified as fairly good. The efficacy of the GLS lamp is 14 lumens per watt over its intended lifespan of 1000 h.

The filament lamp in its simplest form is a purely functional light source that is unchallenged on the domestic market despite the manufacture of more efficient lamps. The GLS lamp is cheap, easy to replace, and does not require any special device such as a ballast, which is required in fluorescent lamps. But it is the least efficient, as only about 5% of the electrical energy is converted to visible light.  

For example, a 20-watt energy-efficient lamp will give to same light output as a 100-watt GLS lamp. An 11-watt energy-efficient lamp is equivalent to a 60-watt GLS lamp. Energy-efficient lamps also have a lifespan of about eight times longer than a GLS lamp and so, they do use energy very efficiently.

Answer.4. Photometer

Explanation:-

The instrument used to compare the illuminating powers of two sources of light is called the photometer. The following two types of photometers are in common use

1. Bunsen Grease spot Photometer
2. Lummer Brodhum photometer
3. Flicker photometer

The first two are best suited for use if the two sources to be compared give the light of same or approximately similar colors. Increase the light from the two sources to be compared differ in color, a flicker photometer is best suited.

Answer.4. Guilds Flicker Photometer

Explanation:-

Flicker photometer

The flicker photometers are employed when two sources give the light of different colors to be compared. The color contrast between two lights does not affect their working is the unit feature of the nicker photometer. l his is because the color contrast between the two alternating fields of the light disappears at a lower speed of alternation than does a contrast of brightness.

A typically used flicker photometer is a Simmance-Abady flicker photometer, where used rotating disc made up of plaster of Paris. The dick is in the form of a double-truncated cone as shown in Fig. The truncated portions of the cone are fitted together to form the disc. The disc is continuously rotated at the required minimum speed by the small motor in between the two sources to be compared. Each half of the disc is illuminated from one source and the eye is presented with the two fields of the light to be compared alternately. When the two halves are having unequal illuminations a flicker appears. Now, the disc is rotated to that position where the flicker disappears. When the two halves of the disc are illuminated equally and then the candlepower of the test source can be calculated by measuring the distances of the disc from the two sources in the usual manner.

Answer.1. Bunsen photometer

Explanation:-

Bunsen grease spot photometer

Bunsen photometer consists of tissue paper, with a spot of grease or wax at its center. It is held vertically in a carrier between the two light sources to be compared. The central spot will appear dark on the side, having illumination in excess when seen from the other side. Then, the observer will adjust the position of the photometer head in such a way that until the semitransparent spot and the opaque parts of the paper are equally bright then the grease spot is invisible, i.e., the same contrast in brightness is got between the spot and the disc when seen from each side as shown in Fig. The distance of the photometer from the two sources is measured. Hence candlepower of the test source is then determined by using the relation:

The CP of the test lamp = the CP of the standard lamp × (L₂/L₁)²

The use of two reflecting mirrors above the photometer head makes it perhaps the accurate method since the two sides of the spot and position of the head can be viewed simultaneously.