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Page 227 #’s 1-7
1. In your notebook, match the description in column A with the correct term in
column B.
Description
• the point where the optic nerve enters the retina
•
attitude of the image in a microscope
•
controls the size of the pupil
•
largest lens in a refracting telescope
•
path from the retina to the brain
•
corresponds to the film in a camera
Item
blind spot
inverted
iris
Objective lens
optic nerve
retina
2. Describe how the distance between the object and the convex lens affects the
characteristics of the image. (4)
• With a convex lens, the size of the image becomes larger as the object moves closer
to the lens. If the object is very close to the lens, then an upright, magnified and
virtual image is formed.
3. Compare the structure and function of the eye of a mammal to the structure and function
of the eyes of several different species. (4)
• Answers will vary depending on what species you chose.
4. How are convex lenses and concave mirrors used in telescopes? (5)
• There are two kinds of telescopes: refracting and reflecting. In a refracting
telescope, light from a distant object is collected and focused by a convex lens
called the objective lens. A second lens, called the eyepiece lens, works as a
magnifying glass to enlarge the image. In a reflecting telescope, there is a concave
mirror acting as the objective instead of a convex lens. This is called the objective
mirror. The eyepiece lens stays the same.
5. Describe how convex lenses are used in microscopes. (5)
• In a microscope, two convex lenses are used. One is called the objective lens and it
produces an inverted, enlarged, and real image. The other convex lens, called the
eyepiece, acts as a magnifying glass and produces a virtual, enlarged, and upright
image of the real image. However, since the real image is inverted compared with
the object, the virtual image is also inverted compared with the object.
6. Give some examples of how optical devices have furthered scientific knowledge. (5)
• Microscopes have provided much knowledge about:
 cells and how they function
 bacteria and viruses
 how the strength and hardness of metals is affected by crystals.
• Telescopes have provided much knowledge about:
 our sun and the objects in our solar system, such as planets, comets and
asteroids
 different types of stars and their organization into galaxies
7. Look at the diagram on the right and explain how binoculars work. (5)
• A pair of binoculars consists of two reflecting telescopes mounted side by side, one
for each eye. Between each pair of lenses is a pair of prisms. The prisms allow the
light rays to be reflected several times off their surfaces. Thus, the prisms greatly
reduce the length of the binocular tubes, making them easier to carry.