Ray Optics Experiment

SKU: E02

1. Online Guidance

The field of ray optics (or geometric optics) is a very old one indeed. The first written work attributable to a scholar in this field is Euclid’s Optica, circa 3rd century BCE. His approach to optics was strikingly similar to his approach to geometry, starting with a set of axioms from which he made deductions. Euclid described the law of reflection and how light travels in straight lines. He studied perspective and how proximity can affect the angle an object subtends at the eye. The field of optics has grown much since then, with a good history of research behind it. Today, optics is no less important in everyday life. From the camera in your smartphone to the high-speed internet connection over fiber-optic cables (which are widely available today) to the widespread use of LASERs in every practical setting, optics has wedged itself deep into our modern lives.

Objective

In this experiment you will become familiarized with the basic principles of optics and how to make calculations based on them. You will encounter the law of specular reflection, Snell’s Law, and total internal reflection. Additionally, you will learn the operating principles of thin lenses.

Description

The description of light as rays is a simple but highly useful one. As long as the scale of optical elements in the system is much larger than that of the wavelength, we can safely treat light as rays. We can use this framework to prove various facts regarding light, among which are the law of specular reflection and Snell’s law.

Using two of the prisms, you will make measurements to verify that light reflects at exactly the same angle as it is incident. In this experiment, we will also verify that the bulk of the reflecting body is not consequential to reflection.

Figure 1 A schematic of specular reflection.

The semicircular prism will serve to exhibit Snell’s law and total internal reflection. We may exploit the geometric properties of the semicircular prism to measure both directions of refraction – from air to higher index medium, and vice versa – depending on its orientation relative to the incoming beam. We will verify Snell’s Law:

and calculate the refractive index of our prisms by employing the following setups.

Figure 3 Setups for verification of Snell's Law experimentally. (Left) From air to a higher index medium. (Right) From a higher index medium to air.

We will employ the semicircular prism one more time in order to exhibit total internal reflection by the following setup:

Figure 4 Setup for total internal reflection.

Using this setup, we will determine the refractive index of our prism based on the critical angle. Finally, we will use the DoE to spread our beam into many lesser beams, and we will collimate these beams using our semicircular prism as a lens. Then we will exhibit the behavior of convex and concave lenses using these parallel rays and calculate each lens’s focal length as well as its radii.

Figure 5 An illustration of parallel rays encountering a: (Top) convex lens. (Bottom) concave lens.

2. Examples of Use

High-speed internet is carried today by fiber-optic cables. These cables exploit the phenomenon of total internal reflection to keep a signal from losing power. Light enters an optical medium with a high refractive index shaped into a long cable at an oblique angle. Light is then allowed to propagate inside, each time it hits one of the walls of the cable it is reflected back in its entirety, effectively retaining its optical power and by extension the signal it carries.

3. K-Optics Kit

The K-Optics ray optics experiment is a low-cost solution for a central and fundamental experiment in optics, allowing experiments to incorporate first-hand experience for the student. The kit employs a variety of K-Optics parts, each designed carefully and purposefully to seamlessly integrate into the K-Optics ecosystem.

Figure 6 A K-Optics ray optics experiment setup.

Figure 7: A K-Optics ray optics experiment.

4. Animation

The following animation describes the setup assembly for Optic Table (1x1)

5. List of Elements

6. Safety Guidelines

Do NOT direct the LASER beam toward any person, pets, or other animal eyes nor any other body part.
Do NOT place yourself in a position where your eyes approach the axis of the LASER beam (even with eye protection). Keep beam paths below or above eye level while sitting or standing (as appropriate).
Do NOT place or remove elements while the LASER is operating! To avoid unexpected reflections, turn the LASER off before making changes to the setup.
Do NOT leave an operating LASER unattended.
When working with a Class II LASER (such as this), it is crucial to prioritize safety to prevent any potential risks to eyes and skin. These LASERs emit visible light at low power levels, which may not cause immediate harm but still pose a risk if proper precautions are not taken. Avoid directing the laser beam towards reflective surfaces that could scatter the light, as well eyes and skin of humans or animals. Remember that even though Class 2 LASERs are considered relatively safe, responsible handling and adherence to safety guidelines are paramount to prevent any accidents or injuries.