HOME SCIENCE CHAPTER 3: LIGHTING IN THE HOME Class: X 2017-18 Answer the following questions. 1 What is a foot candle? Ans Light is usually measured in terms of Foot candles. A Foot Candle is the degree of light falling on a flat surface, one foot away from the direct flame of a candle. 2 Why should we avoid matching fabrics inside a shop? Ans Colours change as light changes. Artificial light softens colours. The mercury lamps used in lamps do not have red rays in them. Therefore, in this light red colour does not appear red. They appear blue or purplish. Colours that appear attractive under this artificial light might not be pleasing in the day light. So matching of fabrics must not be done inside a shop. 3 Why are more people using incandescent bulbs these days? Ans Incandescent bulbs are used in table lamps, wall brackets, hanging fixtures and floor lamps. It produces more heat and less light compared to the power used. The ordinary bulb lasts for 750-1000 hours. Therefore, it is used extensively by people. 4 Give suggestions regarding the lighting to be used in different rooms. Ans Kitchen should be particularly well lit. Wall or ceiling light over the working place, tube lights fixed under cabinets and cooking range. Bedroom use local lights. One tube light placed at the top of the dressing table mirror. Lamp for reading in bed should be adjustable so light falls on the book. Study table to have a separate lamp. Bathrooms should have ceiling as well as mirror light fixtures. Living room use general lighting, task lighting for reading and accent lighting to highlight art work etc. Bright light over front and rear entrances is necessary. Big gardens can have flood lights for proper illumination. 6 What is Ecotone light? Why is it so popular these days? Ans Ecotone light is a fluorescent lamp. It is popular because ( Any 2 points) It has an ultra-long life of 10,000 hours. It lasts 10 times longer than standard incandescent bulbs. It saves 80 percent energy as compared to incandescent bulbs 7 What are fixtures? How are they different from fittings? ( 1 )
Ans Fixture is the equipment that is fixed inside a house. Fixtures refer to holder bracket knobs and accessories. Fittings are parts that are fixed to the equipment. Eg. a circular lamp with a golden rim and translucent glass. 8 Discuss the causes of glare. Ans The causes of glare are as follows: i) Brightness of sources: in case of incandescent bulb, the clear glass exposes the brightly lit filament and causes annoyance and blinding effect. ii) The total volume of light: a high wattage lamp may give more than desired light in the direction of the eyes and causes discomfort to the viewer. iii) Location of the field of view: a source of light located close to the eye causes the problem of glare. This can be overcome by screening the source by a shade or a board as is usually done in case of table lamps. iv) Contrast with the background: a light source viewed against a dark background of a wall is very tiring to the eyes. v) Time exposure: eye fatigue is also caused if the light source is within a field of view for a longer period of time as in when we are sitting at work facing a sunny window. 9 How can glare be reduced or prevented? Ans We can use frosted or opalescent glass which diffuse the light and so the light is softened and is also shadow less. 10 Explain the various kinds of artificial lighting. Ans Direct lighting: Here, the light falls directly over an object. Lighting is provided from a source without reflection from other surfaces. The source of light emits the highest percentage of light downward providing the highest foot candles per watt over the areas beneath the light source. This however creates harshness of shadow and causes discomfort, eye fatigue and interferes with clear vision because of glare. Pendant lights and chandeliers that direct light directly onto the surface of a table or countertop are great examples of direct lighting. Indirect Lighting: Here, the light does not shine on the object being viewed but on other surfaces which in turn reflect light and makes the object visible. In this method almost all the beams of light are directed from the source to the wall or ceiling and from there it is reflected and diffused to the other parts of the room. The reflected light is diffused and is soft, uniform and shadow less. Complete indirect lighting should be used only in those rooms where no reading or precise work is done. In case of any critical or important work is to be done, one can use portable lights that emit some light to the ceiling and provide diffused light directly upon the object or the work piece. The thing to remember ion such a case is that the shades of such lamps should not be completely opaque or highly translucent. Also the light source should be located well above the eye level. Semi-direct lighting: Usually the diffused lighting system emit light in fairly equal proportions in all directions and up and down. The fixture providing diffuse lighting is usually of globe variety and made of glass. A glass reflector directs 60 to 90 percent of the light toward the work area, and 10 to 40 percent toward the sides and top of the globe. ( 2 )
Since semi direct lighting requires diffusion of light, to cut down or prevent glare, the globe (light source) should be large and translucent enough to completely conceal the lighting source. The light source can be enclosed in prismatic or opalescent glass. The glass enclosure can also have cuts or opening on top to reflect 10-40% of the light on to the ceiling. Semi-indirect lighting: This type of lighting emits light in maximum percentage upwards to the ceiling for diffusion back downwards. It provides less foot candle per watt in the centre of the room but illumination is spread over a larger area than others and it has less of soft shadow. Structural or translucent glass is used to deflect and diffuse light downwards. General lighting: It provides an area with overall illumination. It is also called ambient lighting and it radiates a comfortable level of brightness, enabling one to see and walk about safely. It can be achieved by using chandeliers, ceiling or wall mounted fixtures, recessed or track lights and lanterns outside the house. A basic form of lighting that replaces sunlight, general lighting is fundamental to a lighting plan. Local lighting: Task lighting helps you perform specific tasks and activities such as reading, writing, sewing, cooking, homework, or balancing your checkbook. Extra fixtures are often placed in task areas. The necessary luminance depends on the character of the task being performed. Task lighting is usually achieved with recessed and track lighting, pendant lighting, portable lamps, or desk lamps. Accent lighting: Also called highlighting, accent lighting draws attention to a particular object, such as artwork, sculpture, plants or bookcases. As part of an interior design scheme, it is used to draw the eye to houseplants, paintings, sculptures and other prized possessions. To be effective, accent lighting requires as least three times as much light on the focal point as the general lighting surrounding it. 11 Why is light important? Ans Light is important as: It is required for visibility. It enhances the beauty of designs and materials in the house. It is required for health. Sunlight produces vitamin D in the body. Proper light is also good for eyesight. Light is needed for different activities like writing, reading, cooking, finding way etc. 12 How can glare from natural sources be reduced? Ans Glare produced by water sources can be cut down by using glare reducing glass or by growing enough shrubbery which cuts off the glare without cutting down the view. Glare from the sky can be reduced by adequate roof overhangs, growing of trees to screen the glare from wall surfaces. 13 Explain the two main sources of light. A Sunlight /Natural light: ( 3 )
B The source of natural light is the sun. Natural light enters the room from doors and windows. The intensity of light in a room is affected by the admittance of light in a room. Use of proper sun reflections in a room. Use of proper surfaces within a room. Control of glare. Artificial light: It includes earthen lamps (diyas), candles, lantern and electricity. Two most common sources of light used in homes are incandescent bulbs, and fluorescent tubes. 14 What is a lumen? Ans A lumen is a measurement of the amount of light emitted by a bulb or a tube. A bulb of higher power consumption (watts) yields more lumens of light and provides better illumination of objects. 15 Explain fixtures and fittings. Ans Fixtures: Fixture is the equipment that is fixed inside a house. Fixtures refer to holder bracket knobs and accessories. Light fixtures include chandelier, crystal hanging, pendants, night lights, picture lights, post mount light fixtures, round, oval and wall mounted. Fittings: Fittings are parts that are fixed to equipment for example a circular lamp with golden rim and translucent glass. The type of fixtures and fittings should complement the style and look good. How the fittings distribute light will depend on where you put them and whether you conceal or make a feature of them. Switches play an important role in aesthetics, function and ergonomics. More light passed through transparent shades than opaque ones which give more localized pools of light. 16 What are the sources of artificial light? Explain. Ans Incandescent bulb: Is used in table lamps, wall brackets, hanging fixtures and floor lamps. It produces more heat and less light compared to the power used. Lasts for 750-1000 hours. Hence more people use fluorescent tubes. The filament inside the tungsten filament bulb could be: Clean : gives bright light but creates shadow and glare Pearl: glass of this bulb is milky so illumination is soft and is used in the house. Silica: bulbs coated with silica gives soft light. Coloured lamps used for decoration. Fluorescent tubes: They are long cylindrical tubes which emit 3-4 times more light than tungsten bulb of equal wattage. Used mainly in homes as a source of indirect lighting for general illumination. Life of 7500 hours. Turning the light on and off constantly shortens its life. These tubes emit relatively high lumens and light distribution is better along the length of the tube. ( 4 )
Ecotone: Ecotone light is a fluorescent lamp. It has an ultra-long life of 10,000 hours. It lasts 10 times longer than a standard incandescent bulb. It saves 80 percent energy as compared to incandescent bulbs ************************************************************************** ( 5 )
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