Use principles of reflection and refraction to describe how lenses and mirrors work.
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2. Normal
Line
Normal
Line
i
r
i
r
Glass
n = 1.5
Air
n =1.0
r = angle of refraction
i = angle of incidence
Light travels more slowly
in glass than air and
bends towards the normal
when entering glass from air
Light moving from
glass to air
increases speed
and bends away
from the normal
2
8. Waves from a
Distant source
= crest
= trough
Barrier with
Two slits
In phase waves
Emerge from slits
Constructive
interference
Destructive
interference
8
10. VISIBLE AND INVISIBLE LIGHT
• MOST “LIGHT” IS NOT VISIBLE TO THE HUMAN EYE !
• ONLY ABOUT 7 % OF THE KNOWN KINDS OF LIGHT
CAN BE SEEN WITHOUT SPECIAL INSTRUMENTATION.
10
17. Angle of incidence = Angle of Reflection
For each ray
Dotted lines
Shows the
Apparent
Ray source
17
18. Parallel rays
Reflected rays
Virtual focus
Focal length = -
Forms only virtual,
erect, reduced
images between
the virtual focus
and the mirror.
Dotted lines
Shows the
Apparent
Ray focus
18