Integrated Coordinated Science for the 21st Century
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Answers
Physics To Go
- a) Students copy diagram.
b) See diagram in Background Information.
c) The image distance decreases.
d) The image distance increases.
- See chart below.
| Optical Device |
Object Distance |
Image Distance |
Object Size |
Image Size |
| Slide Projector |
0.1 m |
5 m |
0.02 m |
1 m |
| Camera |
3 m |
5 cm |
2 m |
3 cm |
| Telescope |
4 X 108 m |
1 m |
3 X 106 m |
1 cm |
| Photocopy Machine |
10 cm |
10 cm |
25 cm |
25 cm |
| Human Eye |
10 m |
2 cm |
2 m |
0.5 cm |
| Magnifying Glass |
1 m |
10 cm |
30 cm |
4 cm |
a) The object is a slide and the image is projected on a large screen.
b) The object is seen in the viewfinder. The image appears on the film.
c) The object is a celestial object. The image is made inside the telescope.
d) The object is a piece of paper. The image is a copy of that piece of paper.
e) The image is what you are viewing. The image is made on the retina in the inside of your eye.
f) The object is a lampshade. The image is made on a card.
- a) Move the screen closer to the lens.
b) Move the screen away from the lens.
- Real image: slide projector (on the screen), camera (on the film), photocopy machine (on the paper copy), the human eye (on the retina), magnifying glass (on card, if the glass is held more than one focal length from the object virtual image: camera (the viewfinder), magnifying glass (when used as a magnifier).
- a) In an overhead projector.
b) When used as a magnifier.
c) Looking through a concave lens.
- a) Make an image of a distant object and measure the image distance.
b) The one with the shorter focal length.
c) Lens ii has the shorter focal length, since it bends light more. (The light ray from a distant object crosses the lens axis closer to the lens.)
- Just beyond the focus of the lens.
- a) 0.1 m (by substitution into the lens equation).
b) Both must be at twice the focal length, since the object and image distances are equal. Since increasing the object distances reduces the image distance, they are equal at only one point.
- a) 0.087 m
b) Closer to the focus.
(The focus is 0.08 m from the lens.)
c) Even closer to the focus.
d) The image distance will be equal to the focal length.
e) If Do is very large, 1/Do is very small. From the lens equation, that will make the inverse of Di slightly smaller than the inverse of f, so Di itself will be slightly larger than f.
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