Do you enjoy roller skating? How about bowling? Did you know that both of those activities can be much more exciting if done in the dark under a black light? During these times, you can experience the fun of glow-in-the-dark!
Whether you have participated in glow bowling or witnessed the glow-in-the-dark effects of a black light at a skating rink or amusement park funhouse, you are aware of the fascinating and mysterious feeling of seeing your clothes glow as if they were radioactive.
What is happening here? Are black lights magical? No! They are simple tools that utilize science. Let’s take a closer look at black lights and the reason they cause objects to glow.
Black lights are created in a similar way to regular incandescent or fluorescent lights. The primary difference lies in the glass, coatings, or filters used in black lights.
Black lights utilize these different materials so that the majority of the emitted light is ultraviolet (UV) light, with a small amount of visible light in the wavelengths closest to the UV spectrum (indigo and violet). That is why black lights typically appear dark blue or purple.
Ultraviolet light cannot be detected by the human eye. We are exposed to UV light every day when we bask in the sunlight. Although UV light has some enjoyable uses, we must be cautious to avoid excessive exposure, which can lead to an increased risk of skin cancer, eye damage, and aging of the skin.
When UV light reflects off objects that contain specific substances called phosphors, interesting phenomena occur. Phosphors are substances that emit visible light when exposed to radiation.
Phosphors, when hit by UV light, become excited and naturally fluoresce, or in other words, glow. Moreover, although our eyes cannot see the UV light as it leaves the black light, some of the reflected UV light that hits the phosphors loses energy and falls within the visible range. These factors combine to create the familiar glow-in-the-dark effects.
There are various types of phosphors, both natural and man-made. For instance, our teeth and fingernails contain phosphors, which explains why they glow under a black light. Additionally, many man-made phosphors are present in fabrics, paints, and building materials. This is why certain clothing and fluorescent objects appear so fascinating under a black light.
Black lights have numerous practical applications beyond the enjoyment of bowling, dancing, or roller skating. Forensic experts, for example, can utilize black lights to investigate crime scenes for evidence of bodily fluids, such as blood. Law enforcement officers can use black lights to detect counterfeit money, as well as forgeries of antiques and artwork.
Give It a Try
We hope you are filled with Wonder! Remember to explore the following activities with a friend or family member:
- Invite an adult friend or family member to take you on a field trip to a local store that sells a wide range of light bulbs. Check their collection of black light bulbs and, if possible, buy one to conduct your own black light experiments at home!
- Are you a fan of glow-in-the-dark objects and activities? There are various exciting glow-in-the-dark games and activities that you can do at home. Go online and visit Glowing Play for Kids to discover several homemade activities that will make you glow for hours!
- Interested in learning more about the ultraviolet radiation emitted by the Sun? Explore NASA’s online activity on Exploring Ultraviolet (UV) Light from the Sun. Seek assistance from a friend or family member. Take notes on at least three things you learn from the activity.
Wonder Sources
- http://www.physics.org/article-questions.asp?id=66
- http://science.howstuffworks.com/innovation/everyday-innovations/black-light.htm
- http://www.todayifoundout.com/index.php/2012/06/how-black-lights-make-things-glow/
FAQ
1. Why does a black light make things glow?
A black light is a type of ultraviolet (UV) light that emits long-wave UV-A rays. When these rays come into contact with certain substances, they cause them to fluoresce or glow. This happens because the UV-A rays excite electrons in the atoms of these substances, pushing them to a higher energy level. As the electrons return to their original energy level, they release the extra energy in the form of visible light, creating the glowing effect. This phenomenon is particularly noticeable in materials that contain fluorescent pigments or dyes, such as highlighter ink, certain fabrics, and some minerals.
2. Can all materials glow under a black light?
No, not all materials can glow under a black light. The ability of a substance to fluoresce depends on its chemical composition and the presence of certain compounds. Substances that contain fluorescent molecules, such as certain dyes or pigments, are more likely to glow under a black light. However, materials like metals, glass, and most plastics do not typically fluoresce. Additionally, the intensity of the glow can vary depending on the concentration of the fluorescent compounds in the material. Therefore, while many substances can glow under a black light, not all materials will exhibit this effect.
3. Is the glow produced by a black light harmful?
The glow produced by a black light itself is not harmful. Black lights emit UV-A rays, which have longer wavelengths and lower energy compared to UV-B or UV-C rays. UV-A rays are generally considered less harmful to the skin and eyes, although prolonged exposure to high-intensity UV-A light can still cause damage. However, it is important to note that some materials that glow under a black light, such as certain chemicals or substances, may be hazardous or toxic. Therefore, it is always recommended to handle and use substances that fluoresce under a black light with caution and follow proper safety guidelines.
4. What are some practical applications of black lights?
Black lights have various practical applications in different fields. In forensic investigations, black lights are used to detect bodily fluids, fingerprints, or trace evidence that may not be visible under normal lighting conditions. They are also commonly used in the entertainment industry for creating special lighting effects or enhancing the glow of fluorescent materials in performances or themed events. Additionally, black lights are used in certain scientific research and industrial processes, such as detecting leaks in air conditioning systems or in the inspection of artwork for authentication purposes.
5. Can black lights be harmful to the eyes?
While black lights emit UV-A rays, which are considered less harmful than UV-B or UV-C rays, prolonged exposure to high-intensity UV-A light can still be damaging to the eyes. Direct and prolonged exposure to UV-A rays can cause eye irritation, discomfort, and in some cases, may contribute to the development of cataracts or other eye conditions. It is important to use black lights in moderation and avoid staring directly into the light source. If using black lights for an extended period or in close proximity, wearing UV-blocking goggles or sunglasses can provide additional protection for the eyes.
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