A glass of water appears distorted underwater due to the phenomenon of light refraction. Water has a different refractive index than air, which leads to a change in the trajectory of light rays and creates this illusion of distortion.
When light passes from a transparent medium like air to another medium with a different density, such as water or glass, it suddenly changes direction: this is what we call refraction. This phenomenon occurs because the speed of light is not the same everywhere. For example, when you dip a glass into water, the light rays that go from the water to the glass and then back to your eyes follow a slightly twisted path. These changes in direction create an impression of visual distortion, which explains why the glass appears curved, stretched, or even broken under the water, depending on your angle of view.
Refraction directly depends on the indices of refraction of the mediums traversed, here glass and water. Specifically, each material has its own index: about 1.33 for water and around 1.5 for glass. This difference forces light rays to change angle abruptly when passing from one medium to another, thus causing a strange visual effect: a glass placed underwater appears larger, distorted, or shifted compared to what is seen in open air. The greater the difference between the indices, the more significant the refraction and therefore the visual distortion will be. That's why, even without being a magician, you can achieve this cool optical effect simply by dipping your glass underwater.
Light slows down when it passes from air to water, and then from water to glass. Because each material has its own speed of light propagation, the ray bends slightly at each change of medium. The slower the speed in a medium, the more the light ray "dives" or approaches the normal (the line perpendicular to the surface). This difference in speed creates a visual distortion, making the glass of water appear twisted or cut, while in reality, everything remains straight and in place. It is this variation in speed that generates these intriguing optical effects, giving the impression that your spoon is doing a funny underwater dance.
The rounded shape of the glass acts like a lens, further altering the path of light rays and thus enhancing the effect of visual distortion. The more curved a lens is, the more you notice these distortions. A straight or flat lens produces much fewer of these strange illusions. As for the transparency of the glass, it directly affects clarity: a perfectly transparent lens reduces the loss of visual information, allowing for very clear observation of the distortions caused by refraction. But as soon as a lens has imperfections, whether small or large, they further disrupt the path of light and can muddle your perception even more.
Our brain receives the information sent by our eyes, but sometimes it gets tricked. It always assumes that light travels in a straight line, even when there is clearly refraction (the bending of light rays when passing from water to glass to air). As a result, it reconstructs an image from light rays that it perceives as coming from a specific location, when in reality, they have been diverted. This is what gives that strange sensation of distortion of glass underwater. Our visual system simply isn't used to correctly handling these little physical tricks related to changes in medium (water, glass, air). We think we see a glass bent or broken when everything is fine in reality.
Fish often appear distorted or displaced underwater precisely because of the phenomenon of light refraction. This explains why it is often difficult to catch them just by aiming at their apparent position.
Each material has a specific refractive index: for example, diamond has a particularly high index, which explains its unique brilliance by strongly dispersing light.
One can also observe refraction when placing a straw in a glass: the straw appears broken or twisted at the point where air meets water.
Prisms use the principle of refraction of white light to decompose it into a range of distinct colors known as the visible spectrum. This is the same phenomenon that occurs naturally in a rainbow.
It is related to the refractive index. Underwater, light is bent differently, altering the perception of the size and proximity of submerged objects. Generally, submerged objects appear closer and larger due to the refracted path of light rays.
Indeed, colors change underwater: the refraction and progressive absorption of different wavelengths of light cause certain colors (such as red or orange) to disappear quickly, resulting in a dominant appearance of blue or green.
This phenomenon results from light refraction. When light passes from one transparent medium to another (for example, from air to water), it changes speed and direction. Our brain then interprets the glow by visually extending the path of the light rays, which creates an impression of a break or bend in the object.
Sure! Here’s the translation: "Yes, indirectly. The temperature of the water affects its density, which can slightly modify its refractive index. Thus, warm water that is less dense will produce a slightly different refractive index compared to cold water, potentially altering the observed visual effects."
Absolutely! Cloudy water contains more suspended particles, which further disrupt the path of light through scattering and absorption. This diminishes or blurs the net effects of refraction, making objects harder to distinguish clearly and affecting their visual appearance.
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