How Far Does Light Travel Underwater

How Far Does Light Travel Underwater? A large bulk of today’s underwater lights for boats and docks fall short of people’s expectations. Some individuals complain the luminaries look bright, when tested above water, but appear dull when installed underwater.

Generally speaking, there’s probably nothing wrong with the lights. Instead, it is likely the person failed to take into account the density and absorption rate of water.

Dealing with Light Loss

According to scientists, water is roughly 800 times denser, compared to air. Because of this, light gets absorbed in water at a higher rate. This phenomenon contributes to dullness and decreased quality in illumination. Light is absorbed at different rates, as it hits the water. On the surface, a significant amount of sunlight is reflected from the water, which is why looking down at the surface of water can be unbearable during mid-afternoon conditions.

At roughly five meters, red starts to appear fuzzy. Next, at 10-20 meters, orange and yellow start to disappear. At depths of 50 meters, green and blue are only visible. Lastly, at 200 meters, blue disappears, leaving violet as the last remaining color. This is also where the sunlight zone (euphotic) ends and where the twilight zone (dysphotic) begins. There is not enough light in the dysphotic zone to stimulate photosynthesis in plants.

Four major factors that affect light absorption in water includes the following: weather, conditions at the surface, distance of the subject and depth.

In addition to absorption rates, refraction can be an issue for underwater lights. By comparison, air has a refraction index value of 1.0003, while water features a refractive index value of 1.33. This difference is the reason objects appear closer and larger (sometimes up to 25 percent!) underwater.

Solutions for Underwater Illumination

In order to ensure clarity when setting up underwater lights, they have to be very powerful – beyond the capabilities of above-ground luminaries. It might also help to use a more focused beam, such as a spotlight over a floodlight, if the underwater light is intended for long-distance viewing or support. In some cases, multiple beams or light sources might be required to achieve widespread beam configurations, especially in murky water or in bodies of water that experience a lot of waves and movement.

For underwater photographers, flash guns (also known as underwater strobes) are particularly effective in restoring light in images. For best results, underwater photographers may use dual strobes for increased quality and control over beam angles. Moreover, the strobe must be synced with the camera. Click here to purchase LED underwater lights.

Underwater Red LED Lights Can Improve Visibility In Submarines

Not all marine vessels rely on white lights for illumination. Some units, like underwater submarines, use other colors to maximize visibility. This practice can also be applied to covert military operations, as well as discreet patrollers monitoring docks and passageways at night. Why do submarines use Red LED lights?

Transitioning to Darkness

When a submarine is on the surface during the day, it uses normal LEDs or fluorescent tube-style white lights. These luminaries are typically marine grade, offering some form of protection from the ingress of water or corrosive agents (saltwater). Sub operators turn on red light when transitioning to complete darkness. A common configuration consists of mostly red light with very little white light.

Eventually, the control room will be completely engulfed in black. This is to ensure maximum visibility when looking through a periscope. Without a dark room, individuals would be temporary blind looking to a periscope, as their eyes adjust to the nighttime environment. Furthermore, there is a huge risk related to light leakage when using white lights in submarines, even when covers are utilized to prevent light from escaping the vessel.

Why Red LED Lights?

Red light, with a wavelength measurement of 650 nm, provides optimal low-level lighting conditions for marine applications. It is least intrusive on natural, human night vision – without goggles. As a result, less time is wasted on acclimation during nighttime operations. Additionally, human error is greatly reduced when operators are able to clearly see in dark conditions. From a cost perspective, it’s cheaper to install red lights in control rooms, compared to equipping every worker and operator with specially designed goggles. To maximize natural nighttime vision, some sub operators wear a black patch over the eye they use to peek through a periscope.

This practice can also be observed in aviation control towers, movie theaters, observatories and planetariums. Another sector that uses red light is hunting. Like submarines, using red light when tracking or hunting nocturnal animals helps reduce spooking creatures on the field.
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