224 CorYcfrondehce of linage with Oljetf. [BooIcIIL 



the object from the furface is greater than half the ra- 

 dius of the reflector, the image will be inverted, and 

 on the fame fide of the reflector with the object. If 

 the diftance of the object from the reflector is lefs than 

 half the radius, the image will be erect, but on the 

 other fide of the reflector. This is feen in fig. 9, 

 \vhere q r reprefents an object in the fituation above- 

 mentioned, and QJl is its image, idly, The image 

 of an object before a convex fpherical reflector is al- 

 ways erect, as may be feen in fig. 9. 



In plane reflectors images correfpond, and are fi- 

 milar to their objects. It is not fo in fpherical re- 

 flectors, by which an image is made fometimes greater, 

 fometimes fmaller than the object. The concave re- 

 flector has the power of diminifhing and magnifying. 

 "When the diftance of the object from the reflector is 

 greater than the radius, the image is always lefs than 

 the object, for q r : QJl : : C q : C Qj and in that 

 cafe C q being lefs than C Q^, q r muft be lefs than 

 QJR. When the object is between the center and 

 the principal focus, the image is greater than the ob- 

 ject, for now q r being the object, QJl is its image, 

 and C q being lefs than C Q^, the object muft be lefs 

 than its image. When the object is between the 

 principal focus and the reflector the image is greater 

 than the object; for fuppofing qr (fig. 9.) to be the 

 object, and QJl the image, q r : QJl : : T q : T Qj 

 bur T q being lefs than T Q^, q r muft be lefs than 

 QR. When an object is placed before a convex 

 fpherical reflector, the image is lefs than its object ; 

 for (fig. 9.) T Q^ being greater than T q t QJl muft 

 be greater than q r. 



To find whether an object may be feen in a re- 

 factor by a fpectator in any fituation, we draw lines 

 from the eye to the image, and, if thefe lines are cut 

 by the reflecting furface, the image is vifiblc, and the 



part 



