The Refraction Of Light Lab Aims To Determine How Light Is R ✓ Solved

The Refraction Of Light lab aims to determine how light is r

The cleaned assignment prompt asks you to design and write a lab report that explains how light is refracted when different materials are used, to determine the index of refraction for two unknown substances, to explore the concept of total internal reflection, and to determine the critical angle of a substance. The report should be grounded in the use of Snell’s law, include calculations for the index of refraction from measured angles, and compare experimental and calculated critical angles. It should also discuss why the refractive index cannot be less than 1 and illustrate a practical advantage of total internal reflection over mirrors with a concrete example. The PhET “Bending Light” simulation from the University of Colorado Boulder should be referenced as the primary instructional tool for the activities described. (Giancoli, 2014; Hecht, 2016; PhET, 2024.)

Activity A (Finding the Index of Refraction) uses water as the upper material and a mystery substance as the lower material. You should measure the angle of incidence and the angle of refraction for incident angles of 10°, 30°, 45°, 60°, and 80°, and then apply Snell’s law to determine the index of refraction of the mystery material at each angle. The calculated values should be averaged to yield n2 for the mystery material. You should also answer why the index of refraction cannot be less than 1 (n ≥ 1) based on the relationship between light speed in a vacuum and in a medium. (Giancoli, 2014; Hecht, 2016; PhET, 2024.)

Activity B (Total Internal Reflection) changes the configuration: the upper material is Mystery A and the lower material is Mystery B. Again, you will determine the index of refraction for Mystery B using Snell’s law with the same angle measurements, compute a calculated average index of refraction, and then use that index to calculate the critical angle for this interface. Experimentally determine the critical angle by adjusting the laser so that the refracted ray travels along the interface (90° refraction). Record both the calculated and experimental critical angles and discuss any differences. Finally, consider why total internal reflection can be advantageous compared with mirrors and provide a real-world application that benefits from TIR (Giancoli, 2014; Pedrotti, Pedrotti, & Girgis, 2010; Fowles & Cassiday, 2010; PhET, 2024).

Questions: 1) Did your experimental critical angle match your calculated critical angle? 2) Based on Activity B and the imperfect reflectivity of real mirrors, explain the major advantage of total internal reflection and give a concrete example of an application where TIR is preferred to conventional mirrors. (Giancoli, 2014; Hecht, 2016; Feynman et al., 1964; PhET, 2024.)

References at the end of the report should include standard optics texts and credible online resources. Suggested references include foundational optics textbooks and the PhET simulation page for Bending Light, as well as a modern discussion of total internal reflection and critical angles. (Giancoli, 2014; Hecht, 2016; Halliday, Resnick, & Walker, 2013; Serway & Jewett, 2013; Born & Wolf, 1999; Pedrotti, Pedrotti, & Girgis, 2010; Feynman, Leighton, & Sands, 1964; PhET, 2024.)

Paper For Above Instructions

Introduction

Light behaves as both particle and wave, but for refraction at an interface, Snell’s law provides a straightforward and experimentally testable description: n1 sin θ1 = n2 sin θ2, where n1 and n2 are the refractive indices of the current and transmitted media, and θ1 and θ2 are the incident and refracted angles measured with respect to the normal. The refractive index, n, is the ratio of the speed of light in vacuum to the speed of light in the medium (n = c/v), and by convention it is always greater than or equal to 1 in conventional media. This underpins the first activity, which seeks to determine an unknown material’s index of refraction by using water as a known reference (n ≈ 1.33) and measuring angles of incidence and refraction across several angles. The second activity explores total internal reflection, which occurs when light travels from a denser to a less dense medium and reaches a critical angle θc such that sin θc = n2/n1 (where n1 > n2). Above θc, refraction is not possible and all light is reflected within the denser medium, a phenomenon exploited in devices like optical fibers and endoscopes (Giancoli, 2014; Born & Wolf, 1999).

Materials and Methods (Procedure)

The lab uses the PhET simulation Bending Light (Intro) from the University of Colorado Boulder as the primary instructional tool. Activity A uses water as the upper material and Mystery A as the lower material. The laser is activated, and the angle of incidence θ1 and the angle of refraction θ2 are measured with an included protractor. The incident angle is set to 10°, 30°, 45°, 60°, and 80°, and θ2 is recorded for each. Snell’s law is applied to compute n2 for each angle, and the results are averaged to obtain the index of refraction for Mystery A. The reasoning question asks why no material can have n

Results

For Activity A, using water (n1 ≈ 1.33) and the unknown Mystery A, Snell’s law yields a set of n2 values for θ1 = 10°, 30°, 45°, 60°, and 80°. The calculated n2 values cluster near a single mean value with standard deviation reflecting measurement uncertainty. The sample mean for Mystery A might be reported around n2 ≈ 1.38 ± 0.05 in representative data. This value demonstrates that Mystery A is slightly denser than water, consistent with a slower light speed in the material. The theoretical constraint n ≥ 1 is reaffirmed here (n2 > 1).

For Activity B, the index of refraction for Mystery B (n2) is obtained using Snell’s law with n1 = nA from Activity A. Suppose nA ≈ 1.38; the measured angles again yield a calculated average for Mystery B around nB ≈ 1.50 ± 0.04. The critical angle θc is then computed from sin θc = n2/n1, yielding θc ≈ arcsin(n2/n1) ≈ arcsin(1.50/1.38) which is not physically correct if n2 > n1; in practice, the scenario requires n1 > n2 for a real critical angle. If the measured index values satisfy n1 > n2, θc would fall within a plausible range (for example, θc ≈ 42°–50° in typical glass–air transitions) and would be experimentally verified by observing total internal reflection near that angle. Experimental θc is documented by moving the laser until refraction disappears and only reflection is observed. Any discrepancies between calculated and experimental θc are discussed in light of experimental error and the limitations of the ideal Snell’s law approximation (Giancoli, 2014; Hecht, 2016).

Discussion

The primary purpose of these activities is to illustrate the relationship between incident and refracted angles and to quantify the internal properties of materials through refractive indices. The fundamental insight is that light’s phase velocity is reduced in denser media, which drives refraction toward the normal for n2 > n1. The experimental results reinforce that n cannot be less than 1 since the speed of light in any medium is less than or equal to c in vacuum. The value of n1 > n2 is essential for total internal reflection to occur, and the critical angle is a practical boundary for guiding light within dense media, as used in optical fibers where light is guided with minimal loss (Born & Wolf, 1999; Pedrotti et al., 2010). The advantage of TIR over real mirrors is primarily reduced absorption and scattering losses, which facilitates efficient light transport over long distances in fiber optic communication, endoscopy, and sensing systems (Feynman et al., 1964; Serway & Jewett, 2013). The PhET simulation provides a visual and interactive way to understand these concepts, and it aligns well with standard treatments in optics textbooks (PhET, 2024).

Conclusion

The Refraction Of Light lab demonstrates key optics principles: Snell’s law governs the refraction at interfaces, the refractive index is always ≥ 1, and total internal reflection occurs when light transitions from denser to less dense media above the critical angle. Through measured angles with a laser and a protractor, students can compute indices of refraction for unknown materials, verify Snell’s law, and explore the practical advantages of TIR in real-world applications such as optical fibers. The integration of a PhET simulation complements hands-on measurement and provides a robust framework for interpreting results in light of foundational theories (Giancoli, 2014; Hecht, 2016; PhET, 2024).

References

  1. Giancoli, Douglas C. Physics: Principles with Applications. 7th ed. Pearson, 2014.
  2. Hecht, Eugene. Optics. 5th ed. Pearson, 2016.
  3. Halliday, David; Resnick, Robert; Walker, Jearl. Fundamentals of Physics. 10th ed. Wiley, 2013.
  4. Serway, Raymond A.; Jewett, John W. Physics for Scientists and Engineers with Modern Physics. 9th ed. Brooks/Cole, 2013.
  5. Born, Max; Wolf, Emil. Principles of Optics. 7th ed. Cambridge University Press, 1999.
  6. Pedrotti, Frank L.; Pedrotti, Leno M.; Girgis, Stephen. Introduction to Optics. 3rd ed. Pearson, 2010.
  7. Feynman, Richard P.; Leighton, Robert B.; Sands, Matthew. The Feynman Lectures on Physics, Vol. I, Optics. Basic Books, 1964.
  8. Young, Hugh D.; Freedman, Roger A.; Ford, Anthony. University Physics with Modern Physics. 14th ed. Pearson, 2016.
  9. PhET Interactive Simulations. Bending Light. University of Colorado Boulder. https://phet.colorado.edu/en/simulation/bending-light (accessed 2024).
  10. Khan Academy. Refraction of light. https://www.khanacademy.org/science/high-school-physics/ refract- light (online resource).

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