How Far Does Light Travel Underwater

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.