If you are looking to buy a high-power laser or have a laser pointer already, you may wonder exactly how far any specific mW output power will go on a clear line of site. This is because when browsing for the best model, you’ll run into hundreds of different beam colors, power strengths, and design features. Having a little knowledge of what these numbers mean and how color affects the visible range of a laser is incredibly useful.

After all, if you need your laser to be visible at 100 yards in the flush sun, you cannot go with the lowest power out there. Read this article, and you’ll have a much clearer understanding of how milliwatt (mW) Power, color, and beam width impact your laser output.

Basic Science of Laser Beam Propagation

At its core, a laser emits light through a process called stimulated emission, resulting in a highly focused and coherent beam of light. LASER stands for “Light Amplification by Stimulated Emission of Radiation.” A laser beam is incredibly directional, unlike regular light sources, which scatter light in all directions. This characteristic allows the light to stay narrow and level (straight) over long distances. This is why a laser beam appears as a straight line in the night sky for applications like star gazing and astronomy.

Ideal Laser Beam Scenario: Vacuum Travel

In a perfect vacuum, like space, an unimpeded laser beam would theoretically travel indefinitely, only limited by the expansion of the universe and the quantum effects on a photon over immense timescales. Sure, your eyes would lose sight of it at some point about 20 miles out, but the light will continue to travel nonetheless. While on Earth, several factors come into play within our atmosphere, altering a beam’s path.

Atmospheric Attenuation of a Laser Beam

The Earth’s atmosphere is a mixture of gases, particles, and varying temperatures and pressures, all of which interact with and affect the propagation of a laser beam. This interaction, known as atmospheric attenuation, can cause the laser light to scatter, absorb, and refract, diminishing its intensity and visibility over distance.

1. Scattering: Light can bounce off atmospheric particles, spreading the laser beam and reducing its visibility. Rayleigh scattering, predominant in shorter wavelengths, is why shorter wavelength lasers (like 445nm blue or 405nm purple) may not seem as bright over distances.
2. Absorption: Molecules in the air can absorb specific wavelengths of light, converting it to other forms of energy like heat. This effect is more pronounced in specific atmospheric conditions and for certain laser colors.
3. Refraction: Changes in air density, primarily due to temperature gradients, can bend the path of the laser beam, affecting its direction and focus.

Realistic Distances: What to Expect

So, how far can you see a laser beam? For typical laser pointers you find for sale online, the beam can be clearly visible for a few hundred meters under optimal conditions. High-powered lasers can reach further, with their beams visible for several kilometers, albeit with decreasing intensity. The perceived distance also heavily depends on the observer’s location relative to the beam’s path and the surrounding light conditions. In darker environments, the beam appears more distinct and can seem to travel farther.

Here is some guidance on visible range according to power level on 532nm Green Laser Pointers:

• 5mW: 1-2 miles
• 50mW-100mW: 3-5 miles
• 100mW-200mW: 5-8 miles
• 200mW – 500mW: 8-11 miles
• 1000mW+ (1W): 15 miles or more

If you need a laser pointer for geese control, you need a minimum of 500mW+ in green laser light.

Laser Pointer Safety Considerations

But you shouldn’t be considering visibility alone. Addressing the safety implications is crucial to ensure a laser operator’s and spectators’ safety. Powerful lasers can be dangerous, potentially causing eye damage and disorientation, even being able to start a fire with burning lasers 500mW+. There are common sense operation factors to keep in mind to keep your laser use safe:

1. Never aim at aircraft, motor vehicles, or law enforcement or use a laser in a harmful, threatening, or dangerous manner. 
2. Be aware of reflective surfaces and anything or anyone impeding the path of the laser beam.
3. Never look directly down the aperture or barrel of the laser, and never shine directly at anyone.
4. Wear included laser safety goggles for lasers over 200mW in strength.

Getting Help Choosing the Right Laser

The journey of a laser pointer beam is a testament to the intricate interplay between light and our atmosphere. We’ve covered output power versus color and expected range for a variety of handheld options. But that doesn’t mean you may know precisely what you need for your specific laser use. But if you know where to look, you can get expert laser advice and assistance to ensure you’re going with the most suitable laser for whatever you need.

For the best High Power Laser Pointer with over 75 handheld options, look no further than right here with BigLasers.com’s 20 years of laser expertise. Have a question? Need some guidance? Give us a call today:

877-256-6513