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Section 6.2
Extending Human
Check Your Understanding
Vision
Checking Concepts
1.
Make a table that lists the parts of a camera in one column and the function of each part in the
other.
2.
(a) & (b)
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BC Science 8
3.
(a) Which lens in a microscope is responsible for producing a magnified image on the inside of the
microscope that is not seen directly by the person using the microscope?
The objective lens in a microscope produces a magnified image that is not seen directly.
(b) Why is this image produced?
Forming a magnified image inside the body of the microscope gives an opportunity to use
a second lens to magnify the image even further.
4.
List three features of laser light that make it special compared to light from a regular light bulb.
Laser light contains only one wavelength of light. All the light rays are travelling in the same
direction and all the crests and troughs of the light waves are lined up.
5.
List three technological applications for lasers.
Lasers are used in medical procedures to correct vision problems, in telecommunications to
transmit data, and in scanners to read bar codes. Other applications are also acceptable.
Understanding Key Ideas
6.
(a) Explain why telescopes used to study distant galaxies need to have such large mirrors.
Light from distant galaxies is extremely faint. To detect as much of this light as possible, large
mirrors are used.
(b) Give two reasons why a large lens is inferior to a large mirror in a telescope.
A large lens is inferior to a large mirror because it is extremely heavy and because even the
best lenses absorb some light, removing it from the formation of an image.
7.
How is it possible for a fibre optics cable to carry many different signals at one time without the
signals becoming scrambled?
Fibre optics cables can use laser light of many different wavelengths. These light rays are very
easy to separate at the receiving end of the cable.
8.
How is the property of total internal reflection used in the operation of optical fibres?
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BC Science 8
Total internal reflection is a property that results when light that enters one end of the fibre
reflects off the inside walls of the tube and stays inside the fibre, even if the fibre is bent.
9.
How can a laser be used to perform surgery on the inside of an eye without having to cut open the
eye first?
Since the eye permits the passage of light, a laser can be directed through the lens and has an
effect only on the retina at the back of the eye. In this way a detached retina can be welded
into place without physically touching the eye.
On page 229 of your textbook are two photographs, one taken through a telescope and the other through
a microscope. One is of Earth, taken from above the Moon. The other is of common bacteria called E. coli,
which are found in the mouth of every healthy person on Earth. These two viewpoints were unknown to
humans only three generations ago. Reflect on each, select one, and explain why being able to see this
scene might be important to how humans see the world.
The image of Earth as seen from the Moon shows the entire Earth as a single, relatively small
entity. Previous generations of humans may have considered the Earth to be essentially infinite
in size. This meant that damage to Earth would have little lasting effect. For example, throwing
waste into the ocean would never be a problem once it could be diluted enough. This image
shows that the Earth is finite, and prompted one author to call it “spaceship Earth.” The image
of the bacteria reveals a whole world of life on a tiny scale that was unimagined only a few
generations ago. This form of life is a major carrier of disease, and explains how infections can
be transmitted through sneezing and failing to wash hands. Understanding the microbial basis of
transmitted diseases has saved countless lives.
© McGraw Hill Ryerson 2007
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BC Science 8