2. Introductions
● Surveys – help me to get to know you. I won't
'memorise' it, but it helps me to get to know you
now and throughout the year.
● Mind Map:
What is Physics?
Is it useful, and if so why?
What do you know already?
What would you like to learn this year?
● Sculpture: Use half a packet of clay to make
something which symbolises Physics.
3. PHYSICS
● Physics is the study of the laws of the
universe.
● Other Sciences often apply the laws of
Physics, but to think of them this way is
often pointless.
● Physics came out of Astronomy, which is the
oldest academic discipline.
● This year we will cover waves and light,
electromagnetism, energy resources and
radioactivity.
http://en.wikipedia.org/wiki/File:CollageFisica.jpg
4. Housekeeping
● Welcome to the last year of IGCSE Science at
YIS (for everyone).
● Textbooks
Please keep them in your locker and bring them
to class. Sometimes I will ask you to take it
home for homework, and I recommend you do
for revision.
● Any questions?
6. WAVES
● What are waves? What aren't they? Give some
examples.
7. WAVES
A wave consists of oscillations which move
without carrying matter with them.
The oscillations carry energy.
A wave can be used to carry the energy itself, or it
can be used to carry a signal.
8. Pulse
A pulse is a single wave 'bump' or a “disturbance”.
A pulse can easily be sent down a string or spring.
A wave is made of lots of regular pulses.
10. Amplitude
Amplitude determines how much energy the waves have.
More amplitude = brighter light, louder sound etc.
Wavelength = λ = lowercase (Greek) 'lambda'.
What is the relationship between v, f and λ?
http://upload.wikimedia.org/wikipedia/commons/f/fa/Wave.JPG
12. Longitudinal Waves
Longitudinal waves are the opposite of transverse waves.
The direction of propagation is the same as the direction of
vibration in the medium.
https://encrypted-tbn1.google.com/ima
13. Example
Kaoruko is swimming at a beach with waves
constantly coming from the sea. She estimates
that the distance between the wave crests is 6m,
and two wave crests pass her every second. How
fast are the waves travelling?
14. Example 2
Waltteri shouts across the room at Atsu. He
shouts with a low frequency of 5000 Hertz, and
the waves travel at a speed of 340 m/s. What is
the wavelength of Waltteri's voice?
15. Quick Review
● Write a definition in your own words of:
A. Frequency
B. Wavelength
C. Wave speed
D. Amplitude
E. Crest
F. Trough
● State and explain the wave equation, including
explaining why it works.
16. A. What is the time period of a wave if two waves
pass every twenty seconds?
B. What is the frequency of the wave from A?
C. Hard: what is the relationship between time period
and frequency (for any wave)? Write it like a math
equation, using f for frequency and T for time period.
It is ok if you can't do this question :)
17. The speed of sound in air is about three hundred and forty metres per
second.
10. What is the frequency of a sound wave with a wavelength of 6.8
meters?
11. Humans can hear approximately twenty hertz to twenty kilohertz.
Calculate the minimum and maximum wavelengths humans can hear.
12. The speed of light is 300 000 000 (3 * 108) meters per second.
Calculate the wavelength of red light, given that it has a frequency of 500
000 000 000 000 (5 * 1014) Hertz.
18. The Microwave
● Calculate the wavelength of the microwaves in
a microwave oven.
19. Mia is swimming in a wave pool. The wave
generator creates two waves each second, and
they travel at a speed of three metres per second.
A. Will Mia notice the wave crests or troughs?
B. How far apart are two crests or two troughs?
20. Quantity Symbol Formula Unit
Speed/
V
metres per
velocity s = f*λ second (m/s)
f = v/λ Hertz (Hz)
λ
(lambda)
21. ● Explain the difference between transverse and
longitudinal waves (not done yet)
● Examples:
Transverse Longitudinal
22. Virtual Experiment
Go to phet.colorado.edu/web-
pages/simulations-base.html
● Go to Sound and Waves. Choose “Water” (top
left), “one drip” and “no barrier” (centre right).
● Devise an experiment to calculate the speed of
the waves in the water.
23. Wavefronts
● A wave can be drawn as a series of lines, where each
line represents a crest.
● We can also draw them as a line through the middle of
the wave, often called a ray.
● What is the mathematical relationship between the ray
and the wavefronts?
24. Reflection of Waves
● The region two different media meet is called a
boundary.
● At a boundary a wave can reflect.
http://science.jburroughs.org/mschober/w
25. Refraction of Waves
● If a wave enters a
different medium, its The image of
speed will probably soldiers was
change. from Giancoli
● A change in speed Physics, sixth
causes a change in edition, so
direction. cannot be
distributed here.
● Depth of water
changes the speed
of waves.
26. Diffraction
● As waves pass a barrier or through a gap in a
barrier, they spread out.
● The diffraction is generally only noticeable if the
gap is not much larger than one wavelength.
http://innovativescience.blogspot.com/
27. Textbook work
● All questions on page 95.
● Then continue with assignments.
28. Electromagnetic Radiation
● Electromagnetic radiation is a family of waves which are
made of an electric field and a magnetic field interacting
with each other.
● All EM Waves
A. Are transverse Unnecessary
B. Can travel through a vacuum images of a
C. Travel at c, 3*108 m/s magnet and a
Van der Graaf
generator
removed.
29. Speed, Frequency, Wavelength
The velocity is always the same.
● What happens to the wavelength as the
frequency increases?
● What happens to the frequency as the
wavelength increases?
● What is the mathematical relationship between
frequency and wavelength?
31. Electromagnetic Spectrum
Wave Approximate Approximate Uses
Frequency Wavelength
Radio waves 103m
Microwaves 10-2m
Infra Red 10-5m
Waves
Visible Light 5 *10-7m
Ultraviolet Light 10-8m
X Rays 10-10m
Gamma Rays 10-12m
seeing things; for cell phones and for heating things which contain water; transmitting
signals; photographing bones which can't be seen with visible light; remote controls;
identifying genuine or forged documents, and for purification of air and water; to sterilise
food and seeds, and for cancer treatment
32. The words
seeing things; for cell phones and for heating
things which contain water; transmitting signals;
photographing bones which can't be seen with
visible light; remote controls; identifying genuine
or forged documents, and for purification of air
and water; to sterilise food and seeds, and for
cancer treatment
33. Signals
● Electromagnetic waves are used to carry signals.
● A continuous variation is called an analog signal,
whereas digital signals are represented as numbers.
Most early communications devices used analogue,
while most modern devices use digital (exceptions?).
http://news.bbc.co.uk/2/hi/technology/61429
34. Radio Waves
● Radio waves are used to carry signals for radio,
TV and mobile phones.
● Either the frequency or amplitude must be
changed (modulation) to carry the signal.
http://www.softwareforeducation.com/
35. Frequency Bands
● Different frequencies (“bandwidths”) are used for
different applications. They must be managed(as
a resource) to ensure that people don't use the
same frequency in the same place.
http://en.wikipedia.org/wiki/Radio_spectrum
36. Absorption by the Atmosphere
http://en.wikipedia.org/wiki/File:Atmospheric_electromagnetic_opacity.svg
37. The Ionosphere
● The ionosphere is a layer of charged particles in the
upper atmosphere. Medium waves are reflected off the
ionosphere, and this can be used to spread them
around the Earth.
● Microwaves pass through the atmosphere, and can be
reflected off satellites to pass signals around the
Earth.
http://www.indata.com/satellite_basics.h
http://yutok.blogspot.com/2007/09/broadb
38. AM and FM
● AM radio waves can diffract around hills and
mountains, so are best for rural areas.
● FM signals are better quality, and are generally
used in urban areas.
http://scienceaid.co.uk/physics/wa
39. Fibre Optics
● Fibre optics are thin
glass cables which
carry electromagnetic
radiation(IR or visible
light) inside them.
● They are thinner and
lighter than electrical
wire, and lose less
signal over long
distances.
http://upload.wikimedia.org/wikipedia/commons/thumb/4/49/Fibreoptic.jpg/220px-Fibreoptic.jpg
40. This lesson: SOUND
● Sound waves
● Speed of sound
● Noise and vibration
● Pitch and volume (=frequency and amplitude)
● Pages 100-107
● 10A did the bookwork but not experiment
Tuesday (fire drill)
● 10B Wednesday
● 10C Thursday (One slide completed already)
41. Sound
● Sound is a longitudinal wave.
● It can travel through liquids and all gases.
● An oscilloscope can convert sound waves to
visible transverse waves.
● Humans can hear from around 20 Hz to 20
kHz, and the range decreases with range. A
phone can typically carry waves ranging from
300Hz to 3.4kHz.
42. Pitch and Loudness
● Recall humans can hear from 20 Hz to 20 kHz.
● Frequency = pitch
● Amplitude = volume
http://www.sciencelearn.org.nz/Contexts/Th
43. Frequency Ranges
● Drum = 20Hz
● Low note from a singer = 100Hz.
● High note from singer = 1000Hz.
● Whistle = 10 000 Hz.
All images from wikimedia commons.
44. Testing Skype
● Use a tone generator software (tonegen is free
but 'expires' to test the frequency response
range of skype (or your microphone).
45. Noise and decibels (dB)
● Noise is unwanted sound.
● Sound level is measured in decibels (dB).
http://impact.books.officelive.com/Pro
46. Antinoise
● An antinoise plays the a 'opposite' wave to
sound in the air to cancel it out.
● It is difficult because sound comes from all
around and bounces off walls etc.
http://www.themotorreport.com.au/5928/to
47. The Speed of Sound
● Sound is a longitudinal wave.
● Try out the following simulations:
http://www.kettering.edu/physics/drussell/Demos/wa
● http://www.phy.hk/wiki/englishhtm/Lwave.htm
● http://www.cbu.edu/~jvarrian/applets/waves1/lontra
● Sound can travel in many different media.
Which properties of the medium will determine
the speed of sound in it?
●
●
48. Measuring the Speed of Sound
● Load logger pro and open '33 – Speed of Sound'.
● Formative – teacher view.
● Instructions in handout.
● Follow-up activities: Old IGCSE exam questions
(handed out in class).
49. IGCSE June 2008 Question 2
The number of waves per second.
pitch
dolphin
dolphin
51. ● The Sound of Music
http://upload.wikimedia.org/wikipedia/commons/2/22/Octaaf0320w.JPG
52. Musical Notes
● A simple, 'pure' note is a sound wave of a
single frequency, such as that produced by a
tuning fork.
● However, most things which produce sound
(especially musical instruments) produce other
notes, called overtones, which make notes of
the same frequency sound different.
● If two notes are an octave apart, one has
double the frequency of the other.
53.
54.
55.
56. Light
Light is an electromagnetic wave, therefore:
1) It travels at a speed of light.
2) It can travel through a vacuum.
3) As a wave, it can diffract, refract or reflect.
●Light can be drawn as rays, where the ray is perpendicular
to the wavefronts.
●Light (rays) must travel in straight lines.
●The eye detects light (more later). Some things emit light
(eg the sun, light bulbs) while most things we see reflect light
(eg walls, mirrors, the moon.)
http://commons.wikimedia.org/wiki/File:Gluehbirne_2_db.jpg
57. Electromagnetic
Spectrum
Visible light has a
wavelength of
approximately 400 to
750nm
(_________________).
Our eyes are probably
sensitive to these
frequencies because
____________________
_____________________.
http://commons.wikimedia.org/wiki/File:Electromagnetic-Spectrum-Hebrew.png
58. Lasers
● Laser stands for Light
Amplification through Stimulated
Emission of Radiation (not in IGCSE).
● Laser light is all the same frequency
(c________) and all in phase, meaning that the
troughs and crests are all in the same place.
Lasers have many uses:
● Fibre optics (data)
● Medical Operations
● Cds/DVDs
http://commons.wikimedia.org/wiki/File:Laser_show_disco_(2).jpg
60. Holograms
A hologram is a 3D image made using lasers.
They are often added to important documents and
to make forgery more difficult.
http://upload.wikimedia.org/wikipedia/commons/8/85/Rainbow_hologram.jpeg
61. Reflection of Light
● Most objects reflect light but scatter it in all directions.
Mirrors (and other shiny surfaces) reflect light so that
they produce images.
● Reflected rays follow two rules:
ι ρ
θ =θ
1. The angle of incidence equals the angle of reflection.
2. The incident ray, normal and the reflected ray all lie in
the same plane.
Angle of
incidence Angle of
reflection
http://upload.wikimedia.org/wikipedia/commons/b/b2/Ray_optics_diagram_incidence_reflection_an
d_refraction.svg
62. Images from Plane Mirrors
● Plane mirrors form images which are:
1. the same size
2. the same distance from the mirror
3. laterally inverted (left and right swapped).
● A great site below:
http://www.kss.sd23.bc.ca/staff/jstracha/physics_11/course_material/unit8/U08L01/pages/ray7_
64. The Dog at the Beach
It's probably not necessary to load the picture of
the dog that was here :)
65. How the Dog Runs
Sand Sea
http://commons.wikimedia.org/wiki/File:2009-11-19_(31)_Branch,_Ast.JPG
http://commons.wikimedia.org/wiki/File:Dog_retrieving_stick.jpg
http://commons.wikimedia.org/wiki/File:Brittany_Spaniel_Dog.jpg
66. How the Dog Runs
Sand Sea Sand
http://commons.wikimedia.org/wiki/File:2009-11-19_(31)_Branch,_Ast.JPG
http://commons.wikimedia.org/wiki/File:Dog_retrieving_stick.jpg
http://commons.wikimedia.org/wiki/File:Brittany_Spaniel_Dog.jpg
67. Refraction
● When light enters a different
medium, it changes
direction, unless it enters
along the normal (an angle
of incidence of ______).
● As light enters a more
dense medium, it slows http://www.daviddarling.info/images/refrac
down, and bends
____________ the normal.
● As light enters a less dense
medium, it speeds up, and
bends ____________ from
the normal.
68. The Brain
● Recall that the part of the brain which
subconsciously controls the eye 'thinks' that
light always travels in straight lines.
http://www.mikecurtis.org.uk/light3.gif
69. Why Something Looks Bent in Water
http://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Pencil_in_a_bowl_of_water.svg/1000p
-Pencil_in_a_bowl_of_water.svg.png
70. Refraction and Colour
● High frequency light (eg violet) is bent more
than low frequency light (eg red).
● This is why a prism can separate white light into
its different colours.
● This process is known as dispersion.
http://upload.wikimedia.org/wikipedia/commons/0/06/Prism_rainbow_schema.png
72. The Semi-Circular Block
When light is shone towards the centre of
the (semi) circle, the angle if incidence is
always ________.
73. The Critical Angle is the angle for which the
refracted ray has an angle of refraction of 90°.
74. Total Internal Reflection
● When light travels from a MORE dense
medium to a LESS dense medium, it bends
_____ _______ the normal.
● If the refracted light has an angle of refraction
greater than the critical angle, the light is
instead reflected. This is called total internal
reflection.
75. Determining The Critical Angle
● Determine the critical
angle for perspex.
● While you are using the
ray boxes, also observe http://www.one-school.net/Malaysia/Unive
and draw how light
refracts through a
rectangular perspex
block, and the convex
and concave lenses.
79. Convex Lenses
A convex lens can produce a real image.
A real image forms when light leaves an object
and meets somewhere else. The object appears
to be where its image is.
80. Images
An image can be:
●enlarged, diminished or the same size
●upright or inverted
●real (light focusses there) or virtual (light looks
like it focuses there).
81. Real Images
A real image can be focussed onto a screen. The object
appears to be where the image is. If it is bright and clear
enough, a real image can trick the eye (and person) into thinking
that something is really there.
Ray 1: Parallel to the principle axis and Ray 2: Through the optical centre.
through the focus.
principle axis
C F F
Ray 3: Through the closest focus and
then parallel to the principle axis.
http://upload.wikimedia.org/wikipedia/commons/a/af/Pencil_drawing.png
82. Real Images
A real image can be focussed onto a screen. The object appears
to be where the image is. If it is bright and clear enough, a real
image can trick the eye (and person) into thinking that something
is really there.
Ray 1: Parallel to the principle axis and Ray 2: Through the optical centre.
through the focus.
principle axis
C F F
Ray 3: Through the closest focus and
then parallel to the principle axis.
83.
84.
85. Convex Lens Summary
object Image Real Enlarged / Upright / Use (if any)
position position /virtual Diminished Inverted
/ same size
Beyond C
On C
Between C
and F
On F
Between F
and the
Lens
86. CAMERA
Film/
CCD
If the image were a very, very long way away, what
would the distance from the lens to the film be?
http://commons.wikimedia.org/w/index.php?title=File:Person_Outline_2.svg&page=1
87. CAMERA
Film/ CCD
F
At this point, the image of the man is
focussed on the film.
88. CAMERA
Film/ CCD
F
When the man walks closer, the(larger)
image forms behind the CCD.
89. CAMERA
Film/ CCD
F
To keep the image focussed on the
CCD, the lens is moved towards the
man. The image is larger, which makes
sense because the object being
photographed is closer.
90. An Excellent Site to Try Out
● http://www.phy.ntnu.edu.tw/ntnujava/index.php?topi
● In this simulation it's possible to try many
different locations for objects and images.
91. Concave Lenses
● A concave lens is the opposite of a convex lens.
● Light always diverges (spreads out).
● Parallel light rays spread out as if they had come from a point
called a focus.
http://hyperphysics.phy-astr.gsu.edu/h
● Images will always be _______, ______,and ________.
● Concave lenses will not be examined in IGCSE exams.
92. Alternate Names
● Convex lenses are also called converging
lenses (because they converge light).
● Concave lenses are also called diverging
lenses.
● Concave = “going into a cave”.
93. Parallel verses Non-Parallel Rays
DON'T FORGET ARROWS!!
sun
● Objects from a long way away produce (virtually) parallel rays
of light. Light rays from the sun can be considered parallel
because its distance is considered to be ___________.
● Parallel light rays converge at the __________.
Objects nearby produce light rays which are not parallel. Light
rays from an object of finite do will meet at a distance di. This
distance can be found using a ray diagram or calculations.
