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Integrated Coordinated Science for the 21st Century

Active Physics
+ Chapter 4
Let Us Entertain You
Answers
Physics To Go
  1. a - b) See drawing on page 224.
  2. a - b) See drawing on page 225.
  3. a) You see a right-side-up image of yourself and most of the room you are in. If you hold your finger very close to the spoon, you see a right-side-up, reduced image.
    b) You see an upside-down image of yourself. If you hold your finger very close to the spoon, you see a right-side-up, enlarged image.
  4. a) It should be concave, so it will magnify.
    b) One side is concave and the other is convex. The concave side provides magnification. The convex side provides a wider view.
    c) This curved mirror is convex. It provides a wide-angle view, as does the outside of the spoon, so you can see cars out to the side, in what is called the blind spot. But the image is smaller, so cars appear further behind than they actually are.
    d) A dentist uses a curved mirror to get a magnified view of your teeth.
  5. a)
    object distance

    b) As the object distance decreases, the image distance increases.
    c) The greatest object distance (142 cm) is already so large that the image (at 14 cm) is very close to the focus. Doubling the object distance would bring the image even closer to the focus, but the change might be impossible for the students to detect.
    d) The smallest object distance is 15 cm, and the focal length of the mirror is about
    14 cm (see Part (c) above). If the smallest object distance were halved, the object would be within one focal length of the mirror, so there would be no real image.
  6. As the ball swings toward the mirror, the image also swings toward the mirror.
  7. a) The answer depends on whether or not the ball swings through the focus of the mirror. If it does, then while swinging in, the image goes from upside-down to right-side-up and magnified. At the focus, the image fills the mirror.
    b) You could have several balls swinging in concave mirrors with different focal lengths. You could ask a member of the audience to move his or her head like the ball and then report what he or she sees.
  8. The image gradually moves away from the mirror and becomes larger.