1st Year Physics Chapter 10 Notes

• Important 1st year physics chapter 10 mcqs from Punjab Textbook.
• Optical Instruments: in this chapter, some optical instruments that are based on the principles of reflection and refraction, will be discussed. The most common of these instruments are the magnifying glass, compound microscope and telescopes. We shall also study magnification and resolving powers of these optical instruments, The spectrometer and an arrangement for measurement of speed of light are also described. An introduction to optical fibres, which has developed a great importance in medical diagnostics, telecommunication and computer networking, is also included.
• Least distance of distinct vision
• Magnifying power and resolving power of optical instruments
• Important 1st year physics chapter 10 solved exercise from Punjab Textbook.
• Simple microscope: As discussed above a converging or corivex lena call be used to help the eye to see small objects distinctly A watch maker uses convex lens to repair the watches The object is placed inside the focal point of the lens, Thu magnified and virtual image is formed at least distance of distinct vision d or much farther from the lens:
• Let us, now, calculate the magnification of a simple microscope in Fig 10.3 (a) the image formed by the object, when placed at a distance o, on the eye is shown In Fig. 10.3 (b), a lens is placed just in front of the eye and the object is placed in front of the ens in such a way that a vetual image of the object is formed at a distance'd from the eye. The size of the image is now much larger than without the lens. If and o are the respective angles subtended by the object when seen through the lens (simple microscope) and when viewed directly, then angular magnification M is defined as (10.4) When angles are small, then they are nearly equal to their tangents From Fig. 10.3 (a) and (b).
• Compound microscope
• Astronomical telescope
• Spectrometer
• Collimator
• Time table
• Telescope
• Speed of Light
• Introduction of Fire Optics
• Important 1st year physics chapter 10 important long questions from Punjab Textbook.
• Fire optic principles
• Total internal reflection
• Continuous refraction
• Types of Optical Fibers
• Single mode step index
• Multimode step-index fiber
• Multimode-graded index fibre
• Signal transmission and conversation to sound
• Important 1st year physics chapter 10 long questions from Punjab Textbook.
• Losses of power: When a light signal travels along fibres by multiple reflection, some light is absorbed due to impurities in the glass. Some of it is scattered by groups of atoms which are formed at places such as joints when fibres are joined together. Carelut manufacturing can reduce the power loss by scattering and absorption,
• The information received at the other end of a fibre can be inaccurate due to dispersion or spreading of the light signal Also the light signal may not be perfectly monochromatic. In such a case, a narrow band of wave-lengths are refracted in different directions when the light signal enters the glass fibre and the light spreads.
• Fig. 10.18 (a) shows the paths of light of three different wavelengths λιλα and λαλι meets the core-cladding at the critical angle and, and, at slightly greater angles. All the rays travel along the fibre by multiple reflections as explained earlier. But the light paths have different lengths. So the light of different wavelengths reaches the other end of the fibre at different times. The sighal received is, therefore, faulty or distorted.
• The disadvantage of the step-index fibre (Fig. 10.18 a) can considerably be reduced by using a graded index fibre. As shown in Fig. 10.18 (b), the different wavelengths still take different paths and are totally internally reflected at different layers, but still they are focussed at the same point like X and Y etc. It is possible because the speed is Inversely-proportional to the refractive index. So the wavelength 2, travels a longer path than or but at a greater speed.
• Inspite of the different dispersion, all the wavelengths arrive at the other end of the fibre at the same time. With a step-index fibre, the overall time difference may be about 33ns per km length of fibre. Using a graded index fibre.
• Important 1st year physics chapter 10 numericals from Punjab Textbook.