is10_sb_unit_d

The mirror is controlled by computer so that as the Sun moves
across the sky each winter day, the mirror always reflects into the
village. Residents and tourists need not fear that the mirror will set
them aflame or fry them into crisps, even on a hot summer’s day. There
is no magnifying-glass effect in which sunlight is focussed to a point.
The mirror is flat, so that the Sun’s rays are reflected without being
concentrated.
Our understanding of how to control light for applications such as
the mirror in Viganella is based on the orderly way that light reflects.
The science of how light reflects and bends is called geometric optics.
D12 Quick Lab
Mirror Images
Purpose
To observe and count the number of reflections you
can see in two plane mirrors
Materials & Equipment
• 2 plane mirrors
• tape
• felt pen
• protractor
• paper clip
Figure 11.3 Handle glass mirrors carefully.
Procedure
1. Place two mirrors together so that their reflective
surfaces face each other. Attach the tape so
that the mirrors can open into a “V” shape
(Figure 11.3).
2. Use the felt pen to label the mirrors as R for right
and L for left.
3. Using a protractor, set the mirrors on a sheet of
white paper open to an angle of 72°.
4. Bend a paper clip so that it will stand up, and
place it in front of the right mirror.
5. Look into the mirrors, and count the number of
images of the paper clip that you can see in each
of the mirrors. Record your results.
6. Increase the angle between the mirrors to 90°.
Observe and record the number of images of the
paper clip you see in each mirror.
7. Open the mirrors even wider, to 120°. Observe
and record the number of images of the paper
clip you see in each mirror.
Question
8. What is the relationship between the angle of
separation of the two mirrors and the number of
reflections that you see?
Ray diagrams model the behaviour of light in mirrors and lenses.
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