Laser Based Range Specific Detection-Physics-Lab Report, Exercises of Physics

Download Laser Based Range Specific Detection-Physics-Lab Report and more Exercises Physics in PDF only on Docsity! Introduction We know that a convex lens converge a parallel beam of light to its focus “f”. At focus the intensity is maximum. If we reflect the beam backward after passing through the focusing lens, we will get maximum reflected intensity when the reflecting object is at the focus of the lens. This is the property of the system which we utilize in this experiment. We detect object’s range from the intensity of the reflected light. If the reflecting intensity is registered maximum at the detector, then at that moment the object will be at the focus point of the lens system. The object can be any solid. But for different materials, the intensity peak is different. Procedure I took a He-Ne laser and switched it on. Then I aligned it. I took a lens that focused the beam at its focus. I placed a beam splitter at the focus in such a position that it divided the intensity into half, half of which passed straight and half is deviated away from the detector. This is necessary because the laser intensity is large and the range detection experiment will be not very accurate with large intensities because the detector will become saturated for all reflected intensities. Thus no range detection would be possible. Then the half straight going beam is collimated by double lens system. Then this collimated beam is focused by another lens to its focal point “f”. This “f” is used in range specific detection of the objects. In our experiment f=16 cm. thus the reflected intensity will be maximum at this position. I got the following setup. docsity.com Then I took an object (steel, copper, wood and brass) and fixed it in a holder which can slide on a stand towards the lens. I moved the object slowly in steps towards the lens and noted the reflected intensity registered at the detector. The reflected light comes back following the same path it followed to reach there, and then it is diverted by the beam splitter towards the detector. I got the following readings. All readings are on absolute scale and are only for studying the behavior of the intensity whether it is according to the theory or not. For aluminum Distance (cm) Intensity (Volts) 48 85 45 104 42 107 41 110 40 110 38 123 36 126 34 138 32 143 30 138 28 132 27 126 24 114 23 106 docsity.com