Skip to main content

How to construct the Camera Obscura ( Pin Hole Camera)

Make a circular hole in the shutter of a window, from whence there is a prospect of some distance; in this hole place a magnifying glass,
either double or single, whose focus is at the distance of five or six
feet; no light must enter the room but through this glass. At a
distance from it, equal to its focus, place a very white pasteboard,
(what is called a Bristol board, if you can procure one large enough,
will answer extremely well;) this board must be two feet and a half
long, and eighteen or twenty inches high, with a black border round
it: bend the length of it inward to the form of part of a circle,
whose diameter is equal to double the focal distance of the glass. 

Fix it on a frame of the same figure, and put it on a moveable foot, thatit may be easily placed at that distance from the glass, where theobjects appear to the greatest perfection. When it is thus placed, allthe objects in front of the window will be painted on the paper in aninverted position, with the greatest regularity, and in the most
natural colours. If you place a swing looking-glass outside the
window, by turning it more or less, you will have on the paper all theobjects on each side the window.

If, instead of placing the looking-glass outside the window, you placeit in the room above the hole, (which must then be made near the topof the shutter,) you may have the representation on a paper placedhorizontally on a table, and draw at your leisure all the objects reflected.

Observe, the best situation is directly north; and the best time of
the day is noon.


  1. See also


Post a Comment

Popular posts from this blog



In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

  Common Collector Transistor Circuit

In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by


A test  circuit  for determining the  static characteristic  of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits.   To   measure   the   base   and   the   emitter   currents,   milli   ammeters   are connected in series with the base and the emitter circuits. Voltmeters are connected   across the input an…

XII - Ch# 12 : Electrostatics :Solved Numericals

Solution Manual : Mathematical methods for physicists 5th edition Arfken and Weber

DJ VU Reader
Book Description Now in its 7th edition, Mathematical Methods for Physicists continues to provide all the mathematical methods that aspiring scientists and engineers are likely to encounter as students and beginning researchers. This bestselling text provides mathematical relations and their proofs essential to the study of physics and related fields. While retaining the key features of the 6th edition, the new edition provides a more careful balance of explanation, theory, and examples. Taking a problem-solving-skills approach to incorporating theorems with applications, the book's improved focus will help students succeed throughout their academic careers and well into their professions. Some notable enhancements include more refined and focused content in important topics, improved organization, updated notations, extensive explanations and intuitive exercise sets, a wider range of problem solutions, improvement in the placement, and a wider ra…