# Reflection and Mirrors Review

#### Unit 1

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20. Right angle mirrors produce three images of objects. Which of the following is statements is/are true of the middle image?

1. The middle image is the same size as the object.
2. The middle image is the same distance from the mirror as the object.
3. The middle image will exhibit left-right reversal relative to the object.
4. The middle image is a real image.
5. The middle image is an upright image.
6. The magnification of the middle image is -1.
7. When sighting at the middle image, light will reflect twice prior to reaching one's eye.

 Answer: ABEG A is true; like any plane mirror image, the image formed by two mirrors oriented at right angles is the same size as the object. B is true; the middle image is the same distance from the crease of the dual mirror system as the image is from the crease. However, image distances are usually measured as the smallest distance measured perpendicularly to the mirror. For middle images, this distance would be measured to an extended mirror line and it would be the same distance as that from the object to that same mirror. C is false; the middle image, unlike the primary images, does not exhibit this feature of left-right reversal. D is false; the middle image is a virtual image; it is upright and located behind the mirror (like any virtual image). E is true; just look at the middle image and you will see an upright image. F is false; a magnification of -1 means that the image would be inverted (negative M) and the same size as the object (1); the middle image is the same size as the object but it is not inverted. G is true; light will reflect twice - once off each mirror - prior to traveling to the viewer's eye.

Right Angle Mirrors

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21. Two plane mirrors are attached to form a dual mirror system with an adjustable angle. As the angle between the mirrors increases, the number of images _____.

 a. increase b. decreases c. remains the same

 Answer: B Consider two mirrors arranged at a 0-degree angle - parallel to each other. There would be an infinite number of images, one located directly behind the other forming a line which seems to extend forever. Suppose the mirrors are adjusted to a 30-degree angle (see question #29 below). The mirrors would create 5 images of objects placed between the mirrors. Now suppose that the angle is increased to a 90-degree angle (see question #29 below). Finally, suppose the mirrors are adjusted to a 180-degree angle to form a single plane. At such an angle, only one image would be formed. As the angle is increased, the number of images decreases.

Other Multiple Mirror Systems

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22. Which of the following statements is/are true of a virtual image?

1. Virtual images are always located behind the mirror.
2. Virtual images can be either upright or inverted.
3. Virtual images can be magnified in size, reduced in size or the same size as the object.
4. Virtual images can be formed by concave, convex and plane mirrors.
5. Virtual images are not real; thus you could never see them when sighting in a mirror.
6. Virtual images result when the reflected light rays diverge.
7. Virtual images can be projected onto a sheet of paper.

 Answer: ACDF A is true; virtual images are always located behind the mirror. B is false; virtual images are always upright. C is true; a virtual image is reduced in size if formed by a convex mirror; it is magnified in size when created by concave mirrors; it is the same size as the object when created by plane mirrors. D is true; convex and plane mirrors always form virtual images; concave mirrors will form virtual images of objects placed between the focal point and the mirror. E is false; while virtual images are not real, they can be seen if sighted at in the mirror - just consider your plane mirror image which you probably view everyday. F is true. Virtual images result when incident light from the object strikes the mirror, reflects and diverges. The virtual image is located behind the mirror at the spot where the reflected rays would converge if extended behind the mirror. G is false; only real images which are formed in front of mirrors can be projected onto the screen. Virtual images are located behind the mirror where the light does not travel.

Image Characteristics for Plane Mirrors | Image Characteristics for Concave Mirrors | Image Characteristics for Convex Mirrors

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23. Which of the following statements is/are true of a real image?

1. Real images are always located behind the mirror.
2. Real images can be either upright or inverted.
3. Real images can be magnified in size, reduced in size or the same size as the object.
4. Real images can be formed by concave, convex and plane mirrors.
5. Real images are not virtual; thus you could never see them when sighting in a mirror.
6. Real images result when the reflected light rays diverge.
7. Real images can be projected onto a sheet of paper.

 Answer: CG A is false; real images are always located in front of the mirror. B is false; real images are always inverted and never upright. C is true; a real image can be magnified if placed between C and F of a concave mirror; it can be reduced in size if placed beyond C in front of a concave mirror; and it can be the same size as the object if placed at C in front of a concave mirror. D is false; convex and plane mirrors always form virtual images and can never form real images; only a concave mirror can form both types of images. E is false; real images can be seen when sighting at the image location (just like virtual images can). F is false; real images result when reflected light rays converge to a point. G is true; real images (unlike virtual images) can be projected onto a sheet of paper. Because real images form in front of the mirror at the locations where reflected rays converge, the image can be projected onto a sheet of paper if it is placed at this image location.

Image Characteristics for Plane Mirrors | Image Characteristics for Concave Mirrors | Image Characteristics for Convex Mirrors

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24. Which of the following situations would always result in an image which is magnified in size? (NOTE: the symbol "do" is the same as the symbol "s" and the symbol "di" is the same as " s' ".)

1. Concave mirror: di > 0 and do < di
2. Convex mirror: do > 0
3. Plane Mirror: do > 0
4. Concave Mirror: do> R
5. Concave Mirror: do< f
6. Concave Mirror: do> f and do < R

 Answer: AEF A results in a magnified image. If the image distance is greater than 0, then the image is a real image. If the image distance is greater than the object distance, then according to the magnification ratio, the image height must also be equal to the object height. In B and C, a convex and a plane mirror never create a magnified image. Convex mirrors always create images which are reduced in size. Plane mirrors always create images which are the same size as the object. In D, the object is placed beyond the center of curvature of a concave mirror. In such an instance, the image is reduced in size and located between C and F. In E, the object is placed between the focal point and the surface of a concave mirror. At such an object location, the image is virtual, magnified, and upright. In F, the object is placed in between points C and F of a concave mirror. For such an object location, the image is real, magnified, and located beyond the center of curvature.

Image Characteristics for Plane Mirrors | Image Characteristics for Concave Mirrors | Image Characteristics for Convex Mirrors

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25. Which of the following situations would always result in an image which is upright? (NOTE: the symbol "do" is the same as the symbol "s" and the symbol "di" is the same as " s' ".)

1. Concave mirror: di > 0 and do < di
2. Convex mirror: do > 0
3. Plane Mirror: do > 0
4. Concave Mirror: do> R
5. Concave Mirror: do< f
6. Concave Mirror: do> f and do < R

 Answer: BCE In A, the image is real and its distance is further from the mirror than the object. This could only occur when the object is placed between C and F of a concave mirror. For such an object location, the image is real, inverted, and magnified in size. In B, a convex mirror is used. Convex mirrors always produce upright, virtual images. In C, a plane mirror is used. Plane mirrors always produce upright, virtual images. In D, the object is located beyond the center of curvature of a concave mirror. At such an object location, the image would be real, inverted and reduced in size. In E, the object is located in front of the focal point of a concave mirror. At such an object location, the image would be virtual, upright, and magnified. In F, the object is located between the center of curvature and the focal point of a concave mirror; the image would be real, inverted, and magnified.

Image Characteristics for Plane Mirrors | Image Characteristics for Concave Mirrors | Image Characteristics for Convex Mirrors

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26. TRUE or FALSE:

Virtual images formed by mirrors are always upright images.

 a. TRUE b. FALSE

 Answer: A This is a true statement. The image characteristics of being upright and being virtual go hand in hand. If the image is virtual, then it is upright; and vice versa. Only real images are inverted and only inverted images are real.

Image Characteristics for Plane Mirrors | Image Characteristics for Concave Mirrors | Image Characteristics for Convex Mirrors

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