Semen won’t give off light like a glow-in-the-dark sticker, but it does fluoresce. In other words, it absorbs ultraviolet light and re-emits that energy as visible light. Criminal investigators use black lights to detect semen because they’re portable and easy to use.

By definition, ultraviolet light is ‘beyond violet light’ and the visible spectrum that can be detected by the human eye. It cannot, therefore, be seen directly. Detectors that are sensitive to UV convert it into a form that we can see. In this scenario, however, UV light is being emitted, not received.

More complex broadband radiometers are designed to monitor specifically UVA, UVB or UVE (Erythemal) radiation and these are becoming the most widely used type of UV sensor, such as the Kipp & Zonen UVS range of instruments.

Ultraviolet light was discovered by Johann Wilhelm Ritter in 1801 when he noticed that invisible light beyond the optical region of the electromagnetic spectrum darkened silver chloride. He split sunlight using a prism and then measured the relative darkening of the chemical as a function of wavelength.

The most common form of UV radiation is sunlight, which produces three main types of UV rays:

• UVA.
• UVB.
• UVC.

Black light is nothing but UVA light, while UV light is basically composed out of UVA, UVB and UVC. So in other words, black light is UV light(450-100nm), covering the 400-320nm spectrum.

When UV light bounces off objects that contain special substances called phosphors, interesting things happen. Phosphors are substances that emit visible light in response to radiation. Phosphors hit by UV light become excited and naturally fluoresce, or in other words, glow.

A phosphor converts the energy in the UV radiation from a black light into visible light. White T-shirts and socks normally glow under a black light because modern detergents contain phosphors that convert UV light into white light. This makes whites look “whiter than white” in normal sunlight.

It’s that easy. Place a small piece of tape over the LED flash on the back of your iPhone or Android smartphone (will also work on tablets with built-in flashes), which should be close to your rear camera. Paint on top of the tape with blue marker so that it covers the flash.

Ultraviolet light is extremely important for plant growth. In safe doses, ultraviolet light helps plants and crops produce essential plant oils which not only enhance the flavour and smell of fruit but also helps the plants protect themselves from excessive ultraviolet exposure; acting as their own natural sunblock.

This is one of the easiest processes to make a black light with an LED light strip. All you have to do is to purchase a good quality strip light with a remote controller. Your LED light strips will change color when you click the buttons on your remote controller, till you achieve the desired black light color effect.

Most likely it is a poor connection on the Red wire, A standard DVM meter will test LEDS like these, just set to Ohms and place the leads across a red LED and see if it lights up. If that doesn’t do it, reverse lead polarity.

How To Reset LED Strips

1. Plug your LED strips in and turn it on for a few seconds.
2. Turn it off then take out the power adaptor without turning off the remote control.
3. Press and hold the power button for a few seconds then connect the power supply again.