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Sahay Sir > Question Answers > NCERT Exemplar Class 12 > Physics > Chapter 9 - Ray Optics and Optical Instruments > (a) Fig. shows a cross-section of a ‘light pipe’ made of a glass fibre of refractive index 1.68. The outer covering of the pipe is made of a material of refractive index 1.44. What is the axis of the pipe for which total reflection inside the pipe take place as shown. (b) What is the answer if there is no outer covering if the pipe ?

(a) Fig. shows a cross-section of a ‘light pipe’ made of a glass fibre of refractive index 1.68. The outer covering of the pipe is made of a material of refractive index 1.44. What is the axis of the pipe for which total reflection inside the pipe take place as shown. (b) What is the answer if there is no outer covering if the pipe ?

Consider the diffraction pattern for a small pinhole. As the size of the hole is increased