PES Skill Sheets.book - Capital High School

Skill Sheet 25.2: The Human Eye
a. Cornea—refracts and focuses light.
b. Iris—pigmented part of the eye that opens or closes to change
the size of the pupil.
c. Ciliary muscles—contract to change the shape of the lens.
d. Sclera—outer protective covering.
e. Vitreous humor—liquid inside of the eye.
f. Optic nerve—transmits signals from the retina to the brain.
Skill Sheet 25.3: Measuring Angles
Answers are:
Letter Angle Letter Angle
A 56° J 153°
Skill Sheet 25.3: Using Ray Diagrams
1. A is the correct answer. Light travels in straight lines and
reflects off objects in all directions. This is why you can see
something from different angles.
2. C is the correct answer. In this diagram, when light goes from
air to glass it bends about 13 degrees from the path of the light
ray in air. The light bends toward the normal to the air-glass
surface because air has a lower index of refraction compared
to glass. When the light re-enters the air, it bends about
13 degrees away for the light path in the glass and away from
the normal.
As a ray of light approaches glass at an angle, it bends
(refracts) toward the normal. As it leaves the glass, it bends
away from the normal. However, if a ray of light enters a
piece of glass perpendicular to the glass surface, the light ray
will slow, but not bend because it is already in line with the
normal. This happens because the index of refraction for air is
lower than the index of refraction for glass. The index of
refraction is a ratio that tells you how much light is slowed
when it passes through a certain material.
Skill Sheet 25.3: Reflection
1. Diagram at right:
2. The angle of reflection will
be 20 degrees.
3. Each angle will measure 45
degrees.
B 110° K 131°
C 10° L 148°
D 96° M 81°
E 167° N 90°
F 122° O 73°
G 34° P 27°
H 45° Q 139°
I 19°
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g. Retina—thin layer of cells in the back of the eye that converts
light into nerve signals.
h. Choroid—provides oxygen and nutrients to the retina.
i. Lens—refracts and focuses light.
j. Aqueous humor—liquid in the front part of the eye.
k. Pupil—opening in the iris that controls the amount of light
entering the eye.
3. A is the correct answer. Light rays that approach the lens that
are in line with a normal to the surface pass right through,
slowing but not bending. This is what happens at the principal
axis. However, due to the curvature of the lens, the parallel
light rays above and below the principal axis, hit the lens
surface at an angle. These rays bend toward the normal (this
bending occurs toward the fat part of the lens) and are focused
at the lens’ focal point. The rays diverge (move apart) past the
focal point.
4. Diagram:
4. Diagram at right:
5. The angle is 72 degrees.
Therefore, the angles of
incidence and reflection
will each be 36 degrees.
6. The angles of
incidence and
reflection at point A
are each 70 degrees;
the angles of incidence
and reflection at point
B are each 21 degrees.