How Light Varies at Different Times of Day, Seasons and Cloud Cover

Screenshot 2016-07-24 at 3.48.17 PMThe intensity of light varies with latitudes and seasons, which means at different times of the year, the amount of light changes. All solar radiation comes directly from the sun, which according to research has a surface temperature of approximately 5,500 degrees Celsius. This temperature plays a significant role in determining the characteristics of the solar radiation that we receive on earth.

The amount of radiation we receive at the surface of the atmosphere that is closest to the sun is 1370 joules of energy per second per square meter. If we are close to the equator on a cloud-free day, the amount of direct solar radiation we receive on the earth’s surface is about 75 percent. This is because 13% is absorbed by the atmosphere while another 13% is scattered. In terms of joules, direct radiation therefore measures about 1000 joules per square meter per second.

Quality and Quantity of Energy

Inasmuch as the amount of energy we receive is important, the quality of the energy is significant as well. The amount of energy per unit wavelength of solar radiation peaks at a value of approximately 500 nanometers but ranges to about 3000 nanometers. This radiation consists of short wavelengths. The heat emitted by the earth back into space has a wavelength which is greater than 3000 nanometers and thus referred to as long wave radiation.

Effect of Rotation

Because the earth rotates, the full effect of the 1370 joules per square meter per second is not felt at all times of the day. Since the area of a sphere is calculated as 4 x the area of a disc, the average radiation across the earth atmosphere at any one given time is about 340 joules per square meter per second.

This means, on a diurnal basis, an area close to the equator should expect zero radiation on average on a clear day before sunrise and after sunset. At noon, the area should expect about 1000 joules of shortwave radiation per second.

Effect of Revolution

In addition to rotation, the earth also revolves around the sun in a clockwise motion. This revolution happens at an angle of 23.5 degrees relative to the sun. At autumn and spring equinoxes, each section of the earth receives 12 hours of daylight. However, during winter in the northern hemisphere, the daylight hours are substantially reduced. During summer, daylight hours tend to be greater than any season of the year.

Because of a slight offset in the earth orbit, the winters in the northern hemisphere are slightly milder compared to the southern hemisphere for places along the same latitude.

The Effect of Latitude

The farther away a particular latitude is from the equator, the larger the area over which the solar beam spreads. This means, an area lying on a latitude 50 degrees north receives a solar radiation spread that is 35% larger than what the equator receives. Because of the distance solar radiation travels through the atmosphere to reach these latitudes, the amount of solar radiation also decreases.

The Effect of Cloud Cover

Cloud cover has a profound impact on the actual radiation received on the earth’s surface. Even on a day with clear skies, solar radiation loss can measure up to about 25%. The presence of light cloud increases the loss to about 50% while during thicker cloud cover, losses of about 75% can be experienced.

Therefore, the light received from the sun varies with different aspects amongst them the clarity of the skies, earth rotation, and revolution.

Natural and Artificial Light Sources

Taking a Closer Look at Natural and Artificial Light

Inasmuch as we at times take for granted the light from the sun, without it, the earth would be lifeless. Plants would not be able to grow and consequently animals and humans would be left without food. Sunlight is the main source of energy on earth and if this grows dim, the world would turn cold and water would freeze. In order to understand light in its entirety as well as its sources, we need to look at how it works and its effects.

Understanding Light and how it Moves

Light is basically a form of energy given off when something burns. For instance, the sun is a ball of burning gases which in turn gives off light. Light just like waves in a pond travels in ripples. They travel through the air at a speed of 300,000 kilometer per second. This means light from the sun reaches us in approximately 8 minutes (the distance between the earth and the sun is about 150 million kilometers).

Light travels in straight lines known as rays. Each light wave consists of different wavelengths and this is what gives us the colors of light.

Natural Light

The sun is the main source of natural light. Explosions happening at the center of sun produce huge amounts energy which is then released as heat and light. Some of this energy reaches the earth while part Screenshot 2016-07-24 at 3.42.25 PMof it gets absorbed in the atmosphere. The light from the sun is referred to as white light.

In addition to the sun, natural light also comes from the stars. Because of the distance from the earth, light from the stars constitute a small percentage of the total light reaching the earth. The moon is never a source of light, but a reflector of light from the sun.

Some animals have the capacity to produce their own light. This is called bioluminescence. The light from these animals is mainly used to attract other creatures.

Artificial Light

Human beings through scientific inventions have managed to create and control light. The earliest recognizable form of lighting used by man was fire. This came from burning wood and later gas, oil, and candles. Candles are made from tallow or beeswax. Electricity has now taken over as a convenient source of artificial light.

Electricity as we know it today was developed in the 19th century by Thomas Edison and Joseph Swan. These two scientists designed the first electric light bulbs which had a carbon thread known as filament that glowed when electricity flowed through it.

The common types of electric lights include neon lights, fluorescent tubes, and tungsten filament light bulbs. Tungsten filament bulbs are the cheapest of the three and contain a thin metal filament made from tungsten which becomes hot when an electric current flows through it. The yellow-white glow is what gives light. Neon lights on the other hand are commonly used in advertisement. Neon is an inert gas which gives light whenever high voltage electricity is passed through it. Different colors can be produced by simply varying the electricity current.

Fluorescent tubes are mainly used in homes and offices. The tubes contain mercury vapor which gives off UV light whenever electricity current is passed through it. The UV light is then absorbed by the phosphor powder which coats the inner part of the tube. This results into a glow that produces blue white light.

These are the only known sources of light, but with scientific inventions in top gear, only the future can tell what more will be added.

Understanding Halogen, Fluorescent and LED Lights

There are three main types of lighting solutions the general public can utilize which include LED, fluorescent, and halogen incandescent lamps. Each of these solutions is unique and has its own pros and cons. Before making a decision on which type of lighting to use, the below discussion can be an eye opener and enable you to make a well informed and educated decision.

Incandescent Lamps

These lamps were the first to be created in the early 19th century. Incandescent lamps produce light by Screenshot 2016-07-24 at 3.34.45 PMheating a filament wire which is inside the lamp until it gives a glow. Electricity is the source of this heating. Due to its low production cost, simplicity of integration, and compatibility with both DC and AC, it is one of the most widely used forms of lighting in residential, commercial, and automotive applications.

These lamps are usually filled with an inert gas such as nitrogen or argon to help reduce the evaporation of the filament due to overheating. Halogen lamps use bromine or iodine which combines with the filament wire to create what is known as a halogen cycle. As a result of this cycle, the evaporated materials are re-deposited back into the filament wire and this enhances the lifespan of this lighting solution.

Fluorescent Lamps

Instead of a tungsten wire filament, fluorescent lamps make use of mercury vapor. The vapor inside the Screenshot 2016-07-24 at 3.36.19 PMlamp is stimulated by an electric current to produce ultraviolet light. The inside of the lamp or tube is normally coated with phosphor which absorbs the vapor and begins to glow. The method by which these lamps produce light is known as fluorescence.

Compared to incandescent lamps, fluorescent lamps are much more efficient and last longer. The efficiency of lighting solutions is normally measured in terms of lumen output to watt power consumed. These lamps can exceed 100 lumens per watt of power consumed. In order to turn on the light, fluorescent lights require a starter. The mercury vapor atoms first must be ionized in order for the fluorescence process to begin.

Fluorescent lamps come in different colors because the combination and amount of phosphor material inside the lamp can be adjusted to the desired color temperature.

LED Lamps

LED is an abbreviation for light-emitting diode. This lighting solution produces light when an electric current passes through a semiconductor. For applications that require constant and reliable light, LED lights are recommended.

The efficiency of LED lamps in converting electricity into light is very high. An average quality LED bulb Screenshot 2016-07-24 at 3.38.09 PMcan have an efficacy rate of more than 90 lumens per watt of power consumed. LED diodes are small and compact and this allows them to be used in a number of locations and integrated into existing fixtures without the need for massive modifications.

By changing the color of the semiconductor, you can have different colors of light. It doesn’t matter how frequent you turn these lights on and off, their lifespan cannot be affected. They can last up to 50,000 hours. A number of LED lights made in 1970s and 80s are still working up to date.

How Light Looks When Viewed from Outside and Inside

Whether you are doing interior décor or landscaping, having the knowledge of how light looks indoors and outdoors can give you an advantage in picking lighting solutions. It is in the public domain that if you mix red, blue and green colors, you get a brownish color. However, when you mix red, blue, and green light, you come up with white. The difference may be strange but it is due to the fact that white light is a mixture of various amounts of red, blue, and green light.

When you wear a white t-shirt outside, your eyes see white and if you wear it inside, there is no change. This is because irrespective of where you wear it, your eyes see the same white.

The Kelvin Scale

The color of light is measured through the Kelvin Scale. This is a scientific temperature scale used to measure the temperature of objects. Compared to the Celsius and Fahrenheit scale, Kelvin scale doesn’t have negative numbers. It begins at absolute zero. For instance, if you heat a carbon rod, it will start glowing orange at about 3,200 Kelvin. Greenish and blue glows are emitted at 4,800 and 5,600 degrees Kelvin respectively.

Your living room could be having incandescent lights which emit low color temperatures of about 2800 to 3400 degrees Kelvin. This light will have a yellow to orange cast. If you walk into an office that is lit with fluorescent tubes, you will see green light. Fluorescent light has a color temperature that ranges between 3400 and 4800 degrees Kelvin. This depends on the type of bulbs used in the fixtures.

Outdoor light, on the other hand, has a blue tint. The temperature of its color averages 5600 degrees Kelvin and can range anything from 5200 to well over 12000 degrees Kelvin. The color temperature of outdoor light is dependent on a number of factors including the angle of the sun, the time of day, and the cloud cover.

Mixed Light

At times, you may find yourself dealing with light that is shining through windows which is then mixed up with light from fluorescent tubes and desk lamps. The easiest way when dealing with this light is to remember the basic color temperatures. Using a color-correction jells, you can easily convert indoor lights to outdoor color temperature lights. For instance, placing a color-temperature-blue jell right in front of the lighting instrument will make the light coming through the blue jell to match the color temperature of the light outdoors.

If you want to use outdoor light and you want the warmer tones of indoor light, you can cover the window with color-temperature-orange jell. This jell will reduce the intensity of light without interfering with its color temperature.

Understanding how light varies from the indoors to the outdoors will help you in striking a balance that would bring out the desired qualities of your interior décor and landscaping. It will also give you the freedom to work with different types of light so as to produce exceptional results.

Different Types of Indoor and Outdoor Lighting

pexels-photo-26943Lighting is an essential aspect to both indoor and outdoor ambiance. By using different intensities of light, you can create different moods and relay different messages. There are different types of indoor and outdoor lighting that you may want to consider based on your preferences and needs.

Indoor Lighting

Indoor lighting is usually accomplished through light fixtures. There is no interior design that is complete without light fixtures or luminaires. Luminaire is basically a device that distributes, transforms, or filters the light emitted from lamps. This device includes all the necessary parts for protecting and fixing the lamps except the lamps themselves. In a number of cases, luminaires may also include circuit auxiliaries complete with the means for connecting them to the respective electric supply.

Types of Indoor Light Fixtures

Light fixtures are classified according to the light function, installation method, and lamp type. In terms of light function, there are five basic types of fixtures which are:

  • Ambient Lighting This type of lighting provides an area with total illumination. It radiates a comfortable level of brightness and allows you to see and walk safely without glare. Ambient lighting is commonly provided by traditional pendant type fixtures, chandeliers, ceiling-mounted fixtures, and down lights. The amount of ambient lighting required will depend on the aspect and general décor of the room. If you want a good lighting plan, having a central source of light in all the room is fundamental.
  • Task Lighting Also known as directional lighting, this type of lighting is geared towards a specific area. As the name suggests, task lighting is useful to help you perform a certain task. There are different ways you can provide task lighting including pendant lighting, undercabinet lighting, recessed and track lighting as well as desk and portable floor lamps.
  • Accent Lighting This is also a directional lighting which adds drama to a place through the creation of visual interest. It is mainly used to draw attention to paintings, house plants, sculptors as well as other priced possessions. You can also use this light to highlight the texture of a stone or brick wall, window treatments, or even outdoor landscaping. This lighting is normally provided by wall-mounted picture lights or recessed and track lighting.
  • Decorative Lighting With this lighting, you draw attention to the light fixtures themselves as well as add character to the place being lit. Examples of decorative lighting for your indoor environment include pendants, sconces, light strips, and chandeliers.

Outdoor Lighting

Outdoor lighting can be instrumental in highlighting the landscape and architecture of your home. It can also make paths navigable at night as well as deter intruders. Below are some of the common types of outdoor lighting:

  • Outdoor Wall Lighting These are mainly used to enhance the curb appeal and landscaping of your home. They do this by providing a source of indirect downlighting and uplighting. Using dimmable LED wall sconces in pairs can add an interesting twist to your garage or patio door exteriors.
  • Landscape Lighting This showcases flowers, shrubs, trees, and plants. Most landscape lighting includes well lights and small spotlights. The beauty with these types of lights is they do not compete with your plants for attention. You can also use landscape lighting to highlight architectural features such as columns.
  • Outdoor Hanging Lights These lighting solutions are commonly used to illuminate and enhance the curb appeal of front doors or porches. Pendant lights can add an interesting design element especially when varied in colors, styles, and materials.
  • Post Lanterns If you want to make a dramatic statement in your outdoor lighting, place post lights at the end of a driveway so as to enhance street-side visibility. Post lights can also be installed around patios, pools, and in backyards.

In addition to the above, you may also want to consider outdoor ceiling lights, deck and step lights, flood lights, as well as cove lighting.