4 Lab 4 Refraction Polarization Interference and Diffraction

實驗 4 : 光的折射、偏振、干涉和繞射 Lab. 4 - Refraction, Polarization, Interference and Diffraction of Light l To observe the various phenomena of light l To study some important foudatmental optical principles. A. Refraction Index of Prism (三稜鏡的折射率) B. Polarization of Light (光的偏振) C. Thin-Film Interference of Air Wedge (空氣楔的薄膜干涉 ) D. Multi-reflective Interference in Glass (玻璃片內多次反 射的干涉) Physics. NTHU MFTai戴明鳳

I. Laser Safety Rulers l Class 1 Lasers 1. A warning sign indicating the laser classification should be placed in a visible location on the laser. l Class 2 Lasers 1. Do not stare at the laser or permit any person to stare at the laser beam. 2. Do not point the laser at a person's eye. Physics. NTHU MFTai戴明鳳

Class 3 Lasers 1. Never aim a laser beam at a person's eye. 2. Use proper safety eyewear if there is a chance that the beam or hazardous specular reflection will expose the eyes. 3. Only experienced personnel should be permitted to operate the laser. Never leave an operable laser unattended if there is a chance that an unauthorized person may attempt to use it. A key switch should be used. A warning light or buzzer should indicate when the laser is operating. 4. Enclose as much of the beam path as possible. 5. Avoid placing the unprotected eye along or near the beam axis as attempted in some alignment procedures since the chance of hazardous specular reflection is greatest in this area. 6. Terminate the primary and secondary beams if possible at the end of their useful paths. 7. Use beam shutters and output filters to reduce the beam power to less hazardous levels when the full output power is not required. 8. Make sure that any spectators are not potentially exposed to a hazardous condition. 9. Attempt to keep laser beam paths above or below either sitting or standing position eye level. 10. Operate the laser only in a well-controlled area. That is, in a closed room with no windows and controlled access. 11. Label lasers with appropriate Class III danger statements and placard hazardous areas with danger signs. 12. Mount the laser on a firm support to assure that the beam travels along the intended path. 13. Assure that individuals do not look directly into a laser beam with optical instruments unless a adequate protective filter is present. Physics. NTHU 14. Eliminate unnecessary specular (mirror-like) surfaces from the vicinity of the laser beam path. MFTai戴明鳳

Class 4 Lasers 1. Enclose the entire laser beam path if at all possible. If this is done, the laser device could be considered to be a less hazardous classification. 2. Confine indoor laser operation to a light-tight room with interlocked entrances to assure that the laser cannot emit when a door is open. 3. Insure that all personnel wear adequate eye protection, and if the laser beam irradiance represents a serious skin or fire hazard that a suitable shield is present between the laser beam and the any persons in the room. 4. Use remote firing and video monitoring or remote viewing through a laser safety shield where feasible. 5. Use beam traverse and elevation stops on outdoor laser devices to assure that the beam cannot intercept occupied areas or intercept aircraft. 6. Use beam shutters and laser output filters to reduce the laser beam irradiance to less hazardous levels whenever the full beam power is not required. 7. Assure that the laser device has a key-switch master interlock to permit only authorized personnel to operate the laser. 8. Install appropriate signs and labels on entrances, switches and anywhere an unauthorized person might mistakenly activate the laser. 9. Remember that optical pump systems may be hazardous to view and that once optical pumping systems for pulsed lasers are charged, they can spontaneously discharged, causing the laser to fire unexpectedly. 10. Use dark, absorbing diffuse, fire-resistant targets and backstops. Physics. NTHU where MFTai戴明鳳 feasible.

A. Refraction Index of Triangular Prism (三稜鏡的折射率) Object: To measure the refraction index of prism. Principle: referred from http: //hyperphysics. phyastr. gsu. edu/hbase/hframe. html, “Light and Vision”, in web site “Hyper. Physics”, hosted by the department of Physics and Astronomy, Georgia State University, GA, US A-1 Refraction of Light Refraction is the bending of a wave when it enters a medium where it's speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media. The amount of bending depends on the indices of refraction of the two media and is described quantitatively by Snell's Law. -be responsible for image formation by lenses and the Physics. NTHU eye. MFTai戴明鳳

Refraction of Light & Index of Refraction Physics. NTHU MFTai戴明鳳

Snell’s Law Total Internal Reflection Physics. NTHU MFTai戴明鳳

Physics. NTHU MFTai戴明鳳

Refraction of Prism Physics. NTHU MFTai戴明鳳

Angle of Minimum Deviation of Prism --Provides a good way to measure the index of refraction of a material. Physics. NTHU MFTai戴明鳳

Applications of Prism l A refracting prism is a convenient geometry to illustrate dispersion and l The use of the angle of minimum deviation provides a good way to measure the index of refraction of a material. l Reflecting prisms are used for erecting or otherwise changing the orientation of an image. l Making use of total internal reflection instead of refraction. Physics. NTHU MFTai戴明鳳

Experimental Procedures 1. Let laser beam horizontally incident to the wall or a white paper which has a distance of about 0. 5 m far away. To mark the position of laser beam. 2. Settle the triangular prism on the optical platform with the U-shaped support device and angular scale disc. To adjust the proper position of prism to locate the path of laser beam. 3. Rotate the prism slowly and observe the deviation path of the refracted laser beam by prism. To mark the beam position when the angle of deviation through a prism is minimum. 4. Prisms are typically characterized by their angle of minimum deviation d. This minimum deviation is achieved by adjusting the incident angle until the ray passes through the Physics. NTHU prism parallel to the bottom of the prism. MFTai戴明鳳

Experimental Procedures 5. To measure the distance of the both positions marked by step (1) and (3), and the distance between the prism and the screen of laser spot. To calculate the angle of minimum deviation, , for the prism based on the formula above. 6. Change the incident angle of laser into the prism and repeat the procedures (2) to (4), to get the other the angle of minimum deviation, . 7. To measure the apex angle of the prism . 8. To determine the refraction index of the prism. Physics. NTHU MFTai戴明鳳

B. Polarization of Light (光的偏振) Physics. NTHU MFTai戴明鳳