Worksheet 1
Optics and light
Standard No. 10A.29.1
Objects:
1- Know that properties of light.
2- Know the types of light beams.
Key words:
Light ‫الضوء‬
Straight lines ‫خطوط مستقيمة‬
Shadow ‫الظل‬
A divergent beams ‫أشعة متفرقة‬
Opaque ‫جسم غير منفذ‬
1)
2)
3)
4)
5)
Ray ‫شعاع‬
Bundle ‫حزمة‬
Beam ‫شعاع ضوئي‬
A parallel beams ‫أشعة متوازية‬
A convergent beams ‫أشعة متجمعة‬
Properties of Light summary
Light travels in straight lines called rays.
A bundle of rays is known as a beam of light (Straight and Narrow).
Light travels much faster than sound
We see things because they reflect light into our eyes
Shadows are formed when light is blocked by an object
Types of light beams
A parallel
beam
A
divergent
beam
A
convergent
beam
Opaque is an object that light cannot get through.
Shadows are places where light is blocked
23
Complete the following sentences:
1- Light travels in ………….……………..lines.
2- Light travels ………….…………………….……………..than sound.
3- Shadows are formed when light is ………… by an object.
4- Types of light beams are …………………….,
…………………and……………….
Tell me why………………….
1. Thunder and lightning start at the same time, but we will see the lightning
first
2. When a starting pistol is fired we see the smoke first and then hear the
bang.
3. We see things
Write properties of light.
1-
………………………………………………………………………………
2- ………………………………………………………………………………
3- ………………………………………………………………………………
4- ………………………………………………………………………………
5- ………………………………………………………………………………
................................................................... ‫ عزيزي المعلم‬:‫ولي األمر‬
...................................................................‫عزيزي ولي األمر‬:‫المعلم‬
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Worksheet
Plane mirror
Standard No. 10A.29.1
Objects:
1- light can be reflected by plane surfaces.
2- Explain how images are formed in plane mirrors.
3- Know the properties of image that formed by plane mirror.
key words
Incident ray ‫شعاع ساقط‬
Normal ‫عمودي‬
Law of Reflection ‫قانون االنعكاس‬
The angle of incidence ‫زاوية السقوط‬
the angle of reflection ‫زاوية االنعكاس‬
reflected Ray ‫شعاع منعكس‬
A virtual image ‫صورة تخيلية‬
A real image ‫صورة حقيقية‬
Upright ‫معتدلة‬
Reversed ‫معكوسة‬
Summary
A virtual image is formed by a plane mirror. The rays reflecting from the
mirror appear to have originated from the location of the virtual image. On a
diagram, a virtual image is usually depicted ‫ترسم‬by a broken (dotted) arrow
.‫امتداد األسهم‬
A real image (formed by other kinds of optical devices) can be focused on a
screen‫يمكن استقبالها على حائل‬, whereas a virtual image cannot. On a diagram, a real
image is usually depicted ‫ترسم‬by a solid arrow.
The characteristics of the image
1.
2.
3.
4.
5.
6.
The image is located behind the mirror.
The image is virtual.( can’t be focused on a screen)
The image is the same size as the object.
The image is upright (erect).
The image is reversed.
The image is situated at the same distance from the mirror as the object.
25
‫صنف في الجدول التالي األجسام التالية حسب إنفاذها للضوء‪:‬‬
‫الخشب ‪ /‬الضباب ‪ /‬الماء ‪ /‬الزجاج ‪ /‬بخار الماء ‪ /‬الحديد ‪ /‬الهواء ‪ /‬الورق‬
‫أجسام شفافة‬
‫أجسام معتمة‬
‫أجسام شبه شفافة‬
‫تسمح للضوء بالنفاذ‬
‫ال تسمح للضوء بالنفاذ‬
‫تسمح لجزء فقط من الضوء بالنفاذ‬
‫صل بخط بين ما هو متناسب‪:‬‬
‫االنعكاس‬
‫‪Reflection‬‬
‫زاوية السقوط‬
‫‪angle of‬‬
‫‪incidence‬‬
‫زاوية االنعكاس‬
‫‪angle of‬‬
‫‪reflection‬‬
‫قانون االنعكاس‬
‫‪law of reflection‬‬
‫‪the angle measured from the reflected ray to the surface‬‬
‫‪normal‬‬
‫الزاوية المحصورة بين الشعاع المنعكس والعمود المقام على السطح‬
‫‪the reversal in direction of a particle stream or wave upon‬‬
‫‪encountering a boundary‬‬
‫ارتداد مسار حركة الجسيمات أو الموجات من على حاجز‬
‫‪angle measured from the ray to the surface normal‬‬
‫الزاوية المحصورة بين الشعاع الساقط والعمود المقام على السطح‬
‫‪the angle of reflection and angle of incidence are equal‬‬
‫زاوية االنعكاس تساوي زاوية السقوط‬
‫اختر من الصفات التالية صفات األخيلة في المرايا المستوية‪:‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫معتدل؛ أي أنه ليس مقلوبا‬
‫مقلوب جانبيا؛ أي أن اليمين يبدو أنه اليسار‪( ،‬معكوسة)‬
‫مقلوب؛ أي أنه ليس معتدال‬
‫طول الخيال ضعف طول الجسم‬
‫وهمي؛ أي يتكون خلف المرآة وال يمكن جمعه على حاجز‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫‪‬‬
‫بعد الخيال عن المرآة ربع بعد الجسم عنها‬
‫طول الخيال يساوي طول الجسم‬
‫حقيقي؛ أي يمكن جمعه على حاجز‬
‫بعد الخيال عن المرآة يساوي بعد الجسم عنها‬
‫معتدل جانبيا؛ أي غير مقلوب جانبيا‬
‫‪Which of the following are properties of virtual images formed by‬‬
‫?‪plane mirrors‬‬
‫‪they are inverted‬‬
‫‪they are upright (erected).‬‬
‫‪they are left-left and right-right consistent‬‬
‫‪they are left-right reversed‬‬
‫‪26‬‬
they are enlarged in size
they are equal in size to the object
they are reduced in size
they are located closer to the back of the mirror than the object is in front of the mirror
they are located as far behind the mirror as the object is in front of the mirror
their frequencies (colors) remain the same
their frequencies (colors) are reversed with their complementary colors
they are formed by converging rays
they are formed by diverging rays
they are considered "cool images"
Homework:
What is meant by?
1- angle of incidence:
2- angle of reflection
3- Reflection
4- law of reflection
................................................................... .................................................................. ‫ عزيزي المعلم‬:‫ولي األمر‬
...................................................... ............ .................................................................. ‫عزيزي ولي األمر‬:‫المعلم‬
27
Uses of curved mirrors
‫استخدامات المرآيا الكرية‬
 Car headlamp plus reflector )‫(المرآيا المجودة بكشافات السيارات وتكون مقعرة‬
 Car wing mirror )‫المرآيا الجانبية في السيارات (مرآيا محدبة‬
 shaving/make-up mirror
 satellite TV aerial
 reflecting optical telescope ‫التلسكوب العاكس‬
 solar furnace ‫الفرن الشمسي‬
1-
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‫‪1- What is the type of the following reflections:‬‬
‫‪…………………………..‬‬
‫‪………………………….‬‬
‫‪2- Write missed data of the following shape:‬‬
‫……………………………… ‪1-‬‬
‫……………………………… ‪2-‬‬
‫……………………………… ‪3-‬‬
‫……………………………… ‪4-‬‬
‫……………………………… ‪5-‬‬
‫……………………………… ‪6-‬‬
‫‪W‬‬
‫‪3- What is the relation between No. 5 and No. 6‬‬
‫‪…………………………………………………………………………………………….‬‬
‫‪ -4‬احسب زاوية السقوط في الحاالت التالية‬
‫‪ )a‬اذا كانت زاوية االنعكاس ‪ 20‬درجة‬
‫‪ )b‬اذا كانت الزاوية بين الشعاع الساقط والمنعكس ‪60‬درجة‬
‫‪ )c‬اذا كانت الزاوية المحصورة بين الشعاع الساقط والمرآه ‪ 25‬درجة‬
‫‪ )d‬إذا كانت الزاوية المحصورة بين الشعاع المنعكس والسطح العاكس ‪ 10‬درجات‬
‫‪29‬‬
Worksheet
Refraction ‫االنكسار‬
Standard No. 10A.29.2
11 F.22.5
Objects:
1- Know that light is refracted as it passes from one medium to another.
2- Explain total internal reflection and its application in fiber optics
Key words:
Refraction ‫االنكسار‬
Dispersion ‫تشتت‬
medium ‫وسط‬
Bend )‫ينحرف (ينحني‬
Boundary ‫حد (سطح) فاصل‬
Reflection ‫االنعكاس‬
the refractive index‫معامل االنكسار‬
angle of refraction ‫زاوية االنكسار‬
Angle of incidence ‫زواية السقوط‬
Snell’s law ‫قانون سنل‬
Refraction
It is bending (turning) of light when it passes from one
medium into another.
Why does light refract?
Because the speed of light is differs in different materials.
How does the light refract?
1- The ray of light bends TOWARDS the normal (the
refracted angle will be smaller).
If the ray of light is moving from
the less dense medium to a more dense
the lower index of refraction to higher index of refraction.
the high speed to low speed
2- The ray of light bends away from the normal (the refracted angle will be smaller).
If the ray of light is moving from
the more dense medium to a less dense
the higher index of refraction to lower index of refraction.
the low speed to high speed
30
Why do objects at the bottom of an aquarium ‫حوض السمك‬filled with water
appear‫ يظهر‬closer ‫ أقرب‬than they actually appear?
31
What is meant by index of refraction
It is the speed of light in a vacuum (c) divided by the speed of light in “medium”
(v)
Problem 1
The speed of light in an unknown medium is measured to be
2.76 x 108 m/s.
(a) What is the index of refraction of the
material
n
medium where
Vacuum
1
c = 2.99792458 x 108m/s?
(b) Does it match any of the materials listed
Air
1.0003
in following Table?
Water
1.33
material
n
Crown Glass
1.52
Salt
1.54
Asphalt
1.635
Ethyl
Alcohol
1.36
Heavy Flint
Glass
1.65
Fused
Quartz
1.4585
Diamond
2.42
Whale Oil
1.460
Lead
2.6
Why the spoon ‫ ملعقة‬looks like it’s broken?
Why does the light refract?
32
Draw the light ray in the second medium.
True or False.
The value for the index of refraction, n, of an optically dense medium is allowed to fall anywhere in the
range between 0 < n < 1.
The speed of light in a vacuum is 3 x 108 m/sec.
Diagram Questions
According to the diagram shown above, which substance, A or B, is the more optically dense
medium?
A
B
According to the diagram shown to the right,
which statement is false?
nA = nB
nB > nC
nC < nD
nD > nA
nB > nD
Which diagram shown below correctly illustrates the path of a monochromatic ray of light through a
triangular piece of glass?
33
Which diagram shown below correctly shows the path of a light beam passing through a rectangular
"air bubble" in a piece of glass?
A
B
C
D
Choose the correct answer:
a) If fused quartz is faster?
The right ray will be
A b c d
b) If (angle of refraction > angle of incidence)
The right ray will be
A b c d
c) If fused quartz is slower?
The right ray will be
A b c d
d) If fused quartz same speed as Medium X
The right ray will be
A b c d
e) If there is (No bending)
The right ray will be
A b c d
What's wrong with this picture?
Calculate Speed of light in alcohol if n = 1.36 (Reference Table)
v = c/n
V = (3x 108)/ 1.36
V = 2.21 x 108 m/s
34
Total internal reflection
The total internal reflection takes place if
i) The angle of incidence is greater than the critical angle C
(C=42 for glass , C=49 for water)
The field of fiber optics depends upon the
total internal reflection of light rays traveling
through tiny optical fibers
Dispersion of light
It is the phenomenon of splitting of a
beam of white light into its constituent
colors on passing through prism.
‫يحلل المنشور الثالثي الضوء األبيض إلى الوان الطيف‬
‫السبعة كما بالصورة‬
Formation of a Rainbow
The small droplets of rain water which remain suspended
in air just after the rains act like a prism. When sunlight
passes through these drops of rainwater, it gets dispersed
and we see the seven colors of the rainbow.
The mirage ‫ السراب‬is caused by the total internal
reflection of light at layers of air of different densities.
In a desert, the sand is very hot during day time and a
result the layer of air in contact with it gets heated up
and becomes lighter. The lighter air rises up and the
denser air from above comes down.
35
Lenses
A convex lens is a lens which is thicker at the
center than at the edges.
A concave lens is thinner at its center.
Fig 3
The curved surface/surfaces of a lens bend the light. Notice the paths of light of
the convex and concave lenses shown below.
A convex lens is a converging lens
Convex lens
A concave lens is a diverging lens
Concave lens
36
The human eye
Our eye is the most important natural optical instrument. The
eyes have a convex lens in them. In the eye ,the real ,inverted
image is focused by changing the shape of the lens.
Long sight
a person who can see distant objects clearly but cannot focus
near object is said to be long sighted .this person should wear
a convex spectacles lens
See fig 1
Short sight
a person who can see near objects clearly but cannot focus
distant object is said to be short-sighted .this person should
wear a concave spectacles lens
See fig below
37