Class 11 Physics Ch 10 Notes

• What is least distance of distinct vision? Give its value. OR What is Near point?
• What is focusing at infinity, length of telescope?
• Define spectrometer. Write its main path. Also write its uses.
• Important class 11 physics ch 10 exercise solutions from Punjab Textbook.
• Write function of collimator in spectrometer: Ans: Function of collimator: The function of collimator to make the rays coming from a nearby source parallel. At one end of the tube a convex lens is fixed and on the other hand an adjustable slit is provided. When slit is just at the focus of convex lens then light rays entering from slit become parallel after passing through the lens.
• Define Total internal reflection. Write the conditions of total internal reflection.
• Important class 11 physics ch 10 question answer from Punjab Textbook.
• Define critical angle and refractive index.
• Define Snell’s Law. Write its mathematical form.
• What are the types of optical fibre? Explain: Ans: There are three type of optical fibre. i. Single mode index fibre ii. Multimode step index fibre iii. Multimode step index fibre (i) Single Mode Step Index Fibre: • It has very thin core about 5µm diameter. • It has a relatively large cladding. • Monochromatic light source is required to send light signals through it. • It can carry more than 14 TV channels or 14000 phone calls. (ii) Multimode Mode Step Index Fibre: • It is the optical fibre in which central core has a large diameter such as 50µm and high refractive index. • It is useful for short distance only. (iii) Multimode Graded Index Fibre: • It is an optical fibre in which central core has high refractive index, its density gradually decreases towards its outer surface. • The diameter of the core ranges from 50µm to 1000µm. • It is used for long range distances. 
• Important class 11 physics ch 10 numerical from Punjab Textbook.
• What do you understand by linear magnification and angular magnification? Explain how a convex lens is used as a magnifier?
• Explain the difference between angular magnification and resolving power of an optical instrument. What limits the magnification of an optical instrument?
• Why would it be advantage to use blue light with a compound microscope?
• One can buy a cheap microscope for use by the children. The image seen in such a microscope have coloured edges, why is this so?
• Describe with help of diagrams, how (a) a single biconvex lens can be used as a magnifying glass. (b) biconvex lenses can be arranged to form a microscope: Ans: For Single Biconvex lens: A biconvex lens is used as a magnifying glass. When object is placed within the focal length of the lens them an erect, virtual and magnified image is obtained. For Biconvex lenses: In compound microscope, when the image formed by the objective lens is within focal length of the eyepiece then a virtual, inverted and magnified image is obtained.
• If a person were looking through a telescope at full moon, how would the appearance of the moon be changed by covering half of the objective lens.
• A magnifying glass gives a five-times enlarged image at a distance of 25 cm from the lens. Find, by ray diagram, the focal length of the lens.
• Draw sketches showing the different light paths through a single-mode and a multi-mode fibre. Why is the single-mode fibre preferred in telecommunications?
• How the light signal is transmitted through the optical fibre?
• How the power is lost in optical fibre through dispersion? Explain.