| Invisible UV (ultraviolet) radiations from sun or other sources can cause sunburn, skin cancer and damage to the eyes. “It is important for us to detect the presence and strength of UV lights so that we can minimize our exposure or protect ourselves by using UV filtering eyeglasses and sunscreen lotions.” | 

“The main problem with the UV light is that it is invisible, so it quietly burns the skin and damages the eyes and we will only notice its harmful effects, when it is already too late. Fortunately there are materials that can easily detect UV light and give us advanced warning. One of such materials is known as UV sensitive beads. Girls use them to make bracelet and they enjoy the vibrant colors they radiate under sunlight. In this project you will use UV sensitive beads in your experiments.”

“Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays. It is named because the spectrum consists of refrangible electromagnetic waves with frequencies higher than those that humans identify as the color violet. UV light is typically found as part of the radiation received by the Earth from the Sun. Most humans are aware of the effects of UV through the painful condition of sunburn. The UV spectrum has many other effects, including both beneficial and damaging changes to human health.”

“Ultraviolet (UV) light has shorter wavelengths than visible light. Though these waves are invisible to the human eye, some insects, like bumblebees, can see them!”

 

 

“The energy produced by the sun is electromagnetic radiation with many different wavelengths. Only a small portion of these wavelengths are visible to the human eye. These visible wavelengths are seen as colors of the rainbow depending on the wavelength. Red has the longest visible wavelength and violet has the shortest visible wavelength. When all the waves are seen together, they make white light.”

“Waves longer than those seen as red, are called infrared.  Waves shorter than violet are called ultraviolet.  Ultraviolet light comes in different lengths too.”

 

“While some sunlight is necessary, too much exposure to the sun's invisible ultraviolet A and B rays can cause sunburn, premature aging of the skin, skin cancer, and other health effects.”

“Exposure to ultraviolet (UV) radiation can harm the eyes and affect vision as well. 
 According to the American Optometric Association (AOA), even on an overcast day, harmful UV rays can cause sunburn of both the skin and the cornea of the eye. Over time, unprotected exposure to the sun can increase the possible risk of certain types of cataracts and potentially damage the retina, which could lead to total blindness.”

·         Dependent variable is the strength of UV light measured as the number of seconds it takes for UV sensitive beads to lose their color after stopping exposure to the UV.

·         Constants are the UV beads used for the experiment

Control variable is the condition of cloud or any natural phenomena that may block the sunlight.

  3.    Early morning immediately after sunrise take your blue beads outside in sunny space, remove the cloth and hold them exposed to the sunlight for 3 minutes. 

  4.    Cover the beads again with the cloth and immediately start taking the time using a stopwatch or regular watch. Quickly bring back the beads in a low light room and wait until the beads loose their color and become white again. Record the number of seconds it took for the beads to become white again. 

  5.    Repeat the steps 2 and 4 once every one hour and record your findings in a table like this:

 

 

2)UV Radiation

 

 

3)UV Light Can Harm your Eyes

 

http://www.visionsource.com/blog/how-does-uv-light-affect-eyesight/