Lab 6. Reflection and refraction of light. Objective: 1. To trace the path of a light ray through a glass prism. 2. To verify the validity of the Snell's Law of refraction > Equipment and Materials: Light and optics table with phosphor - luminescent square and built-in circuitry box Lased module 9-volt UL approved power transformer Triangular prism (45- 45- 90") Graph paper (11" x 17") Magnetic strips. Protractor Theory A prism is defined as a polyhedron with a triangular base and three rectangular lateral surfaces. Prism are used in optic to study the behavior of light when passed through it. The light bends at various angles like an angle of incidence, angle of reflection, angle of refraction, and angle of deviation. reflected ray 8-1 -ayla of indidance For reflection from a flat surface, the angle of incidence is equal to the angle of reflection: 9.=0.. This equation is called the law of reflection. When a light ray strikes a transparent material, part of the light is reflected and the rest passes into the material. The ray that travels into the transparent materials is called refracted ray.The angle of refraction depends on the angle of incidence and the speed of the light into the transparent material. The speed of light in glass, water, diamond, etc., is lower that the speed of light in vacuum (c=3.0 x 10 m/si. The index of refraction (n) of a given material is the quotient between the speed of light in vacuum and the speed of light in that material: Examples of index of refraction for some transparent materials: Vacuum: n = 1.0000 Air: n = 1.0003 Water (liquid): n = 1 33 Water (ice): n = 1.31 Glass: n = 1.50 Diamond: n = 2.42 The Snell's law shows the relation between the incident and refracted angles: n, sin 0, =n, sin 02 When the incidence angle exceeds a critical value, all the light is reflected at the interface between the two mediums and there is not refracted ray. This phenomenon is called: total internal reflection. The total internal reflection occurs only when light is incident from the side with the larger index of refraction. > Procedure Experiment 1: Determine the angle of reflection. 1. Fix a white sheet on a drawing board using magnetic strips. 2. Place the triangular prism resting on its triangular base. Using a pencil, draw the outline of the prism. 3. Draw with your pencil a line normal (perpendicular) to the face of the prism AB. Draw lines at 10', 30", 50" with respect to the normal. (See figure 1) 5. Turn on the laser module 6. Align the laser ray with the lines drew before, and draw lines aligned with the reflected ray. 7. Remove the Prism and measure the angle of the reflected ray with respect to the normal line 8. Fill the table belownex sin 0,=nx sine, n =1.0003 n= watent rup Loser module Graph paper 12. Taking the theoretical value of the index of refraction of the glass prism equal to 1.5. Find the percentage of error of the experimental value of the index of refraction using the expression below % Error =accredited nexperimental x 100% nacardical % Error = Include in your conclusions what you have observed after performing this experiment. Conclusions Write the conclusions of your report based on the results obtained after performing the experiments (how the current change with the change of the voltage and the change of the resistance; percentages of errors obtained, etc.)Incident angle 01 Reflected angle 02 10' 15 (10') 30' 32 (30') 50' 46 (50' Normal Prism Laser module Graph paper Fig. 1 9. In your conclusions write what you have observed about the relation between the incident angle and the reflected angle Experiment 2: Determine the index of refraction of the prism material experimentally. 1. Fix a white sheet on a drawing board using magnetic strips. 2. Place the triangular prism resting on its triangular base. Using a pencil, draw the outline of the prism. 3. Draw with your pencil a line normal (perpendicular) to the face of the prism AB. 4. Draw with your pencil a line 30 from the normal (01). 5. Turn on the laser module 6. Align the laser ray with the line drew before. 7. Draw the emergent ray from face BC of the prism. (See figure 2) 8. Remove the prism. 9. Join the incident point and the emergent point with a line. 10. Measure, with the protractor, the angle of the line drew in previous step with respect to the normal (03). 11. Calculate the index of refraction of the prism using the Snell's Law