REFLECTION OF LIGHT. 389 



point in the luminous object. The proper position for the 

 screen may easily be found by trial. Shield the screen from 

 the direct rays of the flame by a card painted black. The 

 inverted image may be seen by a large class. If the image 

 fall between the mirror and the candle, the screen should 

 be quite small. 



6O7. Description of Real Images Formed 

 by Concave Mirrors. (1.) If the object be at the 

 principal focus there will be no image. Why ? (You can 

 find out by trying a construction for the image ( C05). 

 (2.) If the object be between the principal focus and the 

 centre of curvature, the image will be beyond the centre, 

 inverted and enlarged. The nearer the object is to the prin- 

 cipal focus, the larger and the further removed the image 

 will be. (3.) When the object is at the centre, the image 

 is inverted, of the same size as the object and at the same 

 distance from the mirror. (4.) When the object is not 

 very far beyond the centre of curvature, the image will 

 be inverted, smaller than the object, and between the 

 centre and the principal focus. (5.) When the object is 

 at a very great distance, all of the rays will be practically 

 parallel ; there will be but one focus, and consequently nc 

 image. 



(a.) For each of these five cases construct the images. The third 

 case may be prettily illustrated as follows : In front of the mirror, 

 at a distance equal to the radius of curvature, place a box that is 

 open on the side toward the mirror. Within this box hang an 

 inverted bouquet of bright-colored flowers. The eye of the observer 

 is to be in the position mentioned in 605 (2). By giving the mirror 

 a certain inclination, easily determined by trial, an image of the 

 invisible bouquet will be seen just above the box. A glass vase 

 may be placed upon the box so that it may seem to hold the imaged 

 flowers. 



