We did this with 5 different angles of incidence, and recorded our observations, in order to explore the path of light as it travels from one medium into another. Other common systematic errors include hysteresis or lag time, either relating to instrument response to a change in conditions or relating to fluctuations in an instrument that hasn’t reached equilibrium. Addeddate 2012-09-13 18:23:29 Identifier Physics11SnellsLawExperiment Identifier-ark ark:/13960/t6c264j0n Ocr ABBYY FineReader 8.0 Ppi 300. plus-circle Add Review. Get your answers by asking now. A protractor with measurements to minute of arc would be more accurate. The beaker will have a greater amount of error than the cylinder. Therefore, this experiment provides means of determining Snell’s law from the fundamental principles. Some sources of error to think about: Most materials have an index of refraction which is frequency dependent (i.e., rays of different frequencies refract at slightly different angles –this is … Incomplete definition can be a systematic or random error, depending on the circumstances. 4. • When the angles are small there will be a large percentage error. The Law of Reflection (Snell’s Law) states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of velocities in the two media, or equivalent to the opposite ratio of the indices of refraction: During the course of analyzing our data, we calculated the index of refraction for the plastic lens and thereby the speed of light in the plastic. The materials for this experiment include a He-Ne laser (as the light source), a rotating table mounted on the optical bench, a solid plastic semicircular prism, and a semi-circular dish filled with water. Furthermore, is the angle of the incident light ray (from air) with respect to the normal, while is the angle of the refracted ray in water with respect to the normal. For this reason, it’s best to test using different locations of a sample or take multiple measurements to reduce the amount of error. The angle the wavefront makes with Snell's law, refraction at an interface, refractive index, animations, experimental determination of n. Physics with animations and video film clips. This was repeated for different values of the angle of incidence. This is due to measurement errors when you measured the angles of incidence and angles of refraction. In this experiment, the index of refraction for the perspex is 1.50. (ii) Using the recorded data, draw a suitable graph (iii) Explain how your graph verifies Snell’s law. Use i 2 and r 2 to find n again. To verify Snell's law. SOURCES OF ERROR / PRECAUTIONS. Join Yahoo Answers and get 100 points today. by Snell's Law. A cubic mass is placed inside the wall of a rotating cylinder that rotates with an angular velocity *see photo (cont)? Common errors include; inaccurately measuring refracted and incident angles, incorrectly drawing refracted and incident rays, and incorrectly drawing the block. The accepted value is nglass = 1.52. An astronaut visits each of the following planets. Answer to EXPERIMENT 4: REFRACTION: SNELL'S LAW 1. EXPERIMENT-01 REFRACTION THROUGH GLASS SLAB AIM: To trace the course of different rays of light through a rectangular glass slab at different angles of incidence, measure the angle of incidence, refraction and verify Snell`s law. But don't forget to question the formula also! This is why it’s a good idea to record data sequentially, so you can spot gradual trends if they occur. Snell's Law itself might be wrong, or only valid within a certain range of angles. Since plastic is denser then air, the incident ray will bend away from the normal when it travels through air. You will monitor a reflected and a transmitted ray to decide whether the law of reflection and/or Snell's law of refraction predict your observations adequately. (Refer to diagram below) The index of refraction is defined as the speed of light in vacuum divided by the speed of light in the medium. 4. Determination of some thin lenses properties through experiments. There are quite a few cases in the history of science where scientists applied a law, only to later find out that law itself was wrong. Find the average of the two values of n. Use this average as your measured value of n. Calculate a percent error using the accepted value of n accptd = 1.50 for regular clear glass. The Law of Refraction (Snell’s Law) describes the behavior of a ray of light that passes from one medium into another: n 1 sin 1 = n 2 sin 2 (21.3) where n 1 and n 2 are the indices of refraction for the two media, 1 is the angle of incidence, and 2 is the angle of refraction. This is also why it’s good to take data starting with different specimens each time (if applicable), rather than always following the same sequence. Snell’s law stats that when traveling from a denser to a less dense index, the angle of incidence will be less then the angle of refraction. Does your calculated value agree with the measured value within error? What incomplete definition means is that it can be hard for two people to define the point at which the measurement is complete. Still have questions? Physclips provides multimedia education in introductory physics (mechanics) at different levels. Improvements • Verify Snell’s Law for other materials. If you forget to calibrate a balance or you’re off a bit in the calibration, all mass measurements will be high/low by the same amount. Set the prism on the rotating platform level with the laser beam and set its height so that the beam passes through the center of the prism. You will investigate total … If any three of the four variables in the equation are known, the fourth variable can be predicted if appropriate problem-solving skills are employed. Upon what factors would the refractive index of a medium depend? As the instruments warm up, the measurements may change. A physics 11 experiment on refraction and Snell's Law. Candidates were able to calculate critical angle using appropriate formula. 2. After gathering the equipment needed to perform the experiment, we adjusted the slit mask on the light source … Assuming the index of refraction of air is ni = 1.00, use Snell's law and the sines determined above to find the index of refraction of the glass plate. Some instruments require periodic calibration throughout the course of an experiment, so it’s good to make a note in your lab notebook to see whether the calibrations appears to have affected the data. Even though I repeated my measurements each 3 times it would have been better to use 50g weights because I would have had more measurements and would have been easier to evaluate my results. The experiment consists of a single thin bundle of light rays exiting a light box. Wavefront 1 approaches the interface at an angle. We investigate the law of refraction in Part 4 of this experiment. Snell's law (also known as Snell–Descartes law and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.. materials with di erent n. You can (and should) derive the law that describes the change of di-rection (the "law of refraction", or Snell’s law) using a Huygen’s wavelet construction, as shown here. Data: Sources of Error • Parallax error associated with measuring angles using the protractor. The constant in Snell's law is the ratio of the refractive indices of the two materials n and n'. Instrument resolution is also considered a type of random error because the measurement is equally likely higher or lower than the true value. (v) Use the data to verify Snell’s law of refraction. It is common to use this lab to calculate the index of refraction of the material in question (in your case, the acrylic semicircle), using Snell's Law. The riders have a speed of v. (cont)? Finally, calculate q 3 using Snell’s law again. 2. As the instruments warm up, the measurements may change. So when the data doesn't "fit" the formula, question the data first. Drafts, temperature changes, light/dark differences, and electrical or magnetic noise are all examples of. Rank the order of the gravitational acceleration at the surface of the planets (cont). Using Snell's Law to Predict An Angle Value. The project should include some background information on Snell's law, all the steps taken in the experiments, key experimental results and a conclusion about the experiment (including identification of the unknown solid from the refractive index). When you place a piece of paper on top of a book and let them free fall, they hit the ground at the same time?