- #1
guv
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- 22
- Homework Statement
- Here is the conceptual problem 23-3 (3rd example in chapter 23) on geometric optics from Giancoli's Physics textbook.
Q: Is the photo upside down? Close examination of the photograph on the first page of this Chapter reveals that in the top
portion, the image of the Sun is seen clearly, whereas in the lower portion, the
image of the Sun is partially blocked by the tree branches. Show why the reflection is not the same as the real scene by drawing a sketch of this situation, showing
the Sun, the camera, the branch, and two rays going from the Sun to the camera
(one direct and one reflected). Is the photograph right side up?
- Relevant Equations
- N/A
Answer from the book:
We need to draw two diagrams, one assuming the photo on p. 644
is right side up, and another assuming it is upside down. Figure 23–9 is drawn
assuming the photo is upside down. In this case, the Sun blocked by the tree
would be the direct view, and the full view of the Sun the reflection: the ray which
reflects off the water and into the camera travels at an angle below the branch,
whereas the ray that travels directly to the camera passes through the branches.
This works. Try to draw a diagram assuming the photo is right side up (thus assuming that the image of the Sun in the reflection is higher above the horizon than
it is as viewed directly). It won’t work. The photo on p. 644 is upside down.
Also, what about the people in the photo? Try to draw a diagram showing why
they don’t appear in the reflection. [Hint: Assume they are not sitting at the edge of
the pool, but back from the edge.] Then try to draw a diagram of the reverse (i.e.,
assume the photo is right side up so the people are visible only in the reflection).
Reflected images are not perfect replicas when different planes (distances) are involved.
I do not get the italicized part of the answer, especially the bold part. Not sure if it's because the description is too vague or if I overlooked anything in the answer. I have attached both the camera picture and the cartoon picture for the first part of the answer that makes sense.
We need to draw two diagrams, one assuming the photo on p. 644
is right side up, and another assuming it is upside down. Figure 23–9 is drawn
assuming the photo is upside down. In this case, the Sun blocked by the tree
would be the direct view, and the full view of the Sun the reflection: the ray which
reflects off the water and into the camera travels at an angle below the branch,
whereas the ray that travels directly to the camera passes through the branches.
This works. Try to draw a diagram assuming the photo is right side up (thus assuming that the image of the Sun in the reflection is higher above the horizon than
it is as viewed directly). It won’t work. The photo on p. 644 is upside down.
Also, what about the people in the photo? Try to draw a diagram showing why
they don’t appear in the reflection. [Hint: Assume they are not sitting at the edge of
the pool, but back from the edge.] Then try to draw a diagram of the reverse (i.e.,
assume the photo is right side up so the people are visible only in the reflection).
Reflected images are not perfect replicas when different planes (distances) are involved.
I do not get the italicized part of the answer, especially the bold part. Not sure if it's because the description is too vague or if I overlooked anything in the answer. I have attached both the camera picture and the cartoon picture for the first part of the answer that makes sense.