In the famous scene from “The Lord of the Rings,” Legolas, the elf, claims he can see horsemen 5 leagues away and even tell that their leader is tall. But is this really possible, even with perfect eyesight?
When we see something, light travels from a source, bounces off an object, passes through the lens in our eye, and forms an image on our retina. However, light isn’t just a straight line; it’s a wave. This wave nature of light creates a challenge for both us and Legolas.
Any wave, whether it’s water, sound, or light, spreads out when it goes through a small opening. This spreading is called diffraction, and it causes images to blur. For example, if you use a camera with a very small aperture, the details in the photo can become blurred. Similarly, if you hold a piece of paper close to your eye and try to read past it, the words will look blurry.
The blur that occurs when a small point of light spreads out is known as an Airy disk. The size of this disk depends on the light’s wavelength and the size of the opening you’re looking through. For visible light and a human-sized pupil, diffraction limits us to distinguishing objects larger than about seven one-thousandths of a degree. This means that an object one centimeter in size, 100 meters away, would appear blurred.
When Legolas looked at the riders of Rohan 24 kilometers away, diffraction would have blurred anything smaller than 3 meters to appear about 3 meters in size. So, while he might count the horsemen, he couldn’t accurately judge their heights.
What if Legolas could see in ultraviolet (UV) light? Shorter wavelengths like UV light diffract less, allowing for better detail. If Legolas could see in extreme UV, he might distinguish objects as small as 10 centimeters, almost enough to tell a person’s height. However, air absorbs extreme UV light, making it unlikely he could see that way.
In conclusion, while Legolas’s eyesight is legendary, the science of light and diffraction suggests that even he would have limitations in seeing such distant details.
Try creating your own diffraction patterns using a laser pointer and a CD. Shine the laser onto the CD’s surface and observe the patterns that form on a nearby wall. Discuss how these patterns relate to the concept of diffraction and how they might affect what Legolas could see.
Use the formula for the Airy disk size to calculate how much detail you could see at different distances. Compare your results with the scenario in the article. Discuss how the size of the Airy disk affects our ability to see fine details at a distance.
Use a computer simulation or app that models light diffraction to simulate what Legolas might see at different distances. Adjust parameters like wavelength and aperture size to see how they affect the clarity of distant objects.
Research how some animals see in ultraviolet light and discuss how this might help them in their environment. Compare this to Legolas’s hypothetical ability to see in UV and discuss the limitations mentioned in the article.
Build a small-scale diorama of the scene where Legolas sees the horsemen. Use different materials to represent light waves and diffraction patterns. Present your diorama to the class and explain how diffraction would affect Legolas’s vision.
Light – Light is a form of energy that travels in waves and can be seen by the human eye. – Example sentence: When light passes through a prism, it separates into a spectrum of colors.
Wave – A wave is a disturbance that transfers energy through space or matter, often characterized by its wavelength and frequency. – Example sentence: Sound travels through the air as a wave, allowing us to hear music and voices.
Diffraction – Diffraction is the bending of waves around obstacles or through openings, which can cause patterns of light and dark bands. – Example sentence: The diffraction of light through a narrow slit creates a pattern of bright and dark fringes on a screen.
Image – An image is a visual representation of an object formed by a lens or mirror. – Example sentence: The camera lens focuses light to form a clear image on the sensor.
Retina – The retina is the light-sensitive layer at the back of the eye that detects images and sends signals to the brain. – Example sentence: When light enters the eye, it is focused onto the retina, allowing us to see.
Blur – Blur is the lack of sharpness or clarity in an image, often caused by movement or incorrect focus. – Example sentence: If you move the camera while taking a picture, the image may appear blurred.
Aperture – An aperture is an opening through which light enters a camera or other optical device, affecting the brightness and depth of field of an image. – Example sentence: By adjusting the aperture, photographers can control how much light reaches the camera sensor.
Ultraviolet – Ultraviolet (UV) is a type of electromagnetic radiation with a wavelength shorter than visible light, but longer than X-rays. – Example sentence: Ultraviolet light from the sun can cause sunburn if skin is exposed for too long.
Wavelength – Wavelength is the distance between successive crests of a wave, often used to describe electromagnetic waves like light. – Example sentence: Different colors of light have different wavelengths, with red having the longest and violet the shortest.
Size – Size refers to the dimensions or magnitude of an object or phenomenon, which can affect its properties and behavior. – Example sentence: The size of a telescope’s mirror determines how much light it can collect from distant stars.
