Optical Effects. The following diagram will perhaps explain why the inside part of a spoon represents an inverted image, and the back being the reverse. G H is an object placed at some distance from a concave mirror A B, whose centre is C, and whose principal focus is E. The rays from G fall diverging upon the mirror, and are reflected to a focus at g, where they form an image of the extremity at G; in the same way, a representation of the extremity H will be formed at h, so that a complete but inverted image of C H will be thus formed. The above will explain the inverted image formed in the hollow part of the spoon. The rays from the external parts of the arrow A B flow convergingly along

A a B h upon the mirror, and are reflected long a E and the ray B b along b E, and the image of the object is always seen in the direction in which the rays approach the eye. the reflected image of A B is seen along the lines E A and E A behind the glass. E is supposed to be the eye of a or, and P is the point where the rays from All would meet if the glass had not reflected them, or, properly, had not been there. Convex, mirrors always form mirrors of diminished size, the rays from them coming convergent to the eye of the spectator; or, in Other words, the rays from the object proceed to a virtual or Imaginary focus behind the mirror; theme the in.

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seems to he reflected to the eye; this will explain the reflection on the convex part of the spoon. Two images are seen upon the candlestick in consequence of the concavities and convexities of its surface, each part acting as a concave or convex mirror. Rays passing through a convex surface, diverge, or spread them, and a concave one converges them, or brings them to a point. When a ray of light falls upon any body, it is reflected so that the angle of incidence is equal to the angle of reflection ; and this is a fundamental fact, upon which all the properties of mirrors depend. Let a ray of light, passing through a small hole in a dark room, be reflected upon a plain mirror at equal distances from the point of reflection, and the incident and reflected rays will be at the same height from the surface; the same will happen when the rays are reflected from a convex or concave surface. (See Optical Illusion, p. 122).