In this post, I am sharing Optical Instruments – FSC 1st Year Physics Chapter 10 Notes PDF Download for the students of Intermediate Part 1. This chapter’s name is Optical Instruments . Students can download 11th class chapter 9 Physical Optics Notes PDF in there laptop or mobile. These Physics Notes are for all the boards working under Punjab Board like Gujranwala Board, Lahore Board, Faisalabad Board, Multan Board, Rawalpindi Board, Sargodha Board, DG Kahn Board, and Sahiwal Board. Here are the complete FSC 1st Year Physics Notes PDF chapterwise.
FSC Part 1 Physics Chapter 10 Optical Instruments Notes PDF Download
Define the term least distance of distinct vision.
The minimum distance from the eye at which an object appears to be distinct is called least distance of distinct vision or near point.
The least distance of distinct vision is about 25cm from the eye. If the object is held closer to the eye than this distance the image formed will be blurred and fuzzy. The location of the near point. However changes with age.
Describe the construction of compound microscope and derive an expression for its magnifying power.
The magnification produced by a simple microscope is not sufficient and also does not provide full information about the object. Whenever higher magnification required compound microscope is used
Construction:
it consists of two convex lenses.
i) Objective:
the lens near object called objective. It is a convex lens of short focal length and small aperture
ii) Eyepiece
the lens near the eye is called eyepiece, it is a convex lens of comparatively longer focal length than objective and has large aperture.
Working:
The object of height h placed just beyond the principal focus of the objective. This produced a real and magnified image of height h1 of the object at a place situated within the focal point of the eyepiece. The eyepiece then further magnifies it. In normal adjustment, the eyepiece positioned so that the final image formed at the near point of the eye ar a distance d
Magnifying Power:
The angular magnification M of a compound microscope defined to be the ratio tanqe /tanq, where qe the angle subtended by the final image of height h2 and q is the angle that
the object of height h subtended by the final image of height h2 and q is the angle that the object of height h would subtend at the eye if place at the near point d.
Now
tanq = h/d and tanq = h2/d
thus, magnification M = tanqe /tanq
M = d/h = h2/d x d/h = h2/h
M = h2/h x h1/h1
Whare h1/h is the liner magnification M1 of the objective and h2/h is the magnification M2 of the eye piece, hence total magnification is
M =M1M2
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