Grade 10 Physics

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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.

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

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?

Sculptures

Show and Tell :)

WAVES

What are waves? What aren't they? Give some examples.

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.

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.

A Nice Animation

http://upload.wikimedia.org/wikipedia/commons/7/74/Simple_harmonic_motion_animation.gif

Amplitude

Amplitude determines how much energy the waves have.

More amplitude = brighter light, louder sound etc.

Wavelength = = lowercase (Greek) 'lambda'.What is the relationship between v, f and ?

http://upload.wikimedia.org/wikipedia/commons/f/fa/Wave.JPG

Transverse Waves

https://encrypted-tbn0.google.com/images?q=tbn:ANd9GcTQfDMrJa4Kw3LKud7j9t21lk9914Y7F59pyY5OXJL2r0eh28wphQ

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/images?q=tbn:ANd9GcQR5t6Oj40x-1weZmNDzDCeZA6sv_PnjFXm7ymtMoCgOtXBQ82k_Q

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?

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?

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.

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 :)

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.

The Microwave

Calculate the wavelength of the microwaves in a microwave oven.

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?

QuantitySymbolFormulaUnit

Speed/
velocityVs = f*metres per second (m/s)

f = v/Hertz (Hz)

(lambda)

Explain the difference between transverse and longitudinal waves (not done yet)

Examples:

Transverse Longitudinal

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.

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?

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/waveslite/problem6solution.html

Refraction of Waves

If a wave enters a different medium, its speed will probably change.

A change in speed causes a change in direction.

Depth of water changes the speed of waves.

The image of soldiers was from Giancoli Physics, sixth edition, so cannot be distributed here.

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/2011/02/diffraction.html

Textbook work

All questions on page 95.

Then continue with assignments.

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
B. Can travel through a vacuum
C. Travel at c, 3*108 m/s

Unnecessary images of a magnet and a Van der Graaf generator removed.

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?

The Electromagnetic Spectrum

http://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/EM_Spectrum_Properties_edit.svg/675px-EM_Spectrum_Properties_edit.svg.png

Electromagnetic Spectrum

Wave ApproximateFrequencyApproximate WavelengthUses

Radio waves103mMicrowaves10-2mInfra Red Waves10-5mVisible Light5 *10-7mUltraviolet Light10-8mX Rays10-10mGamma Rays10-12m

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

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

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/6142998.stm

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/wikileki/index.php?title=FM

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

Absorption by the Atmosphere

http://en.wikipedia.org/wiki/File:Atmospheric_electromagnetic_opacity.svg

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://yutok.blogspot.com/2007/09/broadband-internet-via-hf-radio.html

http://www.indata.com/satellite_basics.html

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/waves/radio.html

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

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)

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.

Textbooks

Physics for Higher Tier

Questions on page 95, 97 and 99, 101.

Write answers in the most efficient way for your learning. I will only check completion; they are not 'assignments' and all material is covered in the notes,

This was after sound until Mon 13

Pitch and Loudness

Recall humans can hear from 20 Hz to 20 kHz.

Frequency = pitch

Amplitude = volume

http://www.sciencelearn.org.nz/Contexts/The-Noisy-Reef/Sci-Media/Images/Graphs-of-sound-waves

Frequency Ranges

Drum = 20Hz

Low note from a singer = 100Hz.

High note from singer = 1000Hz.

Whistle = 10 000 Hz.

All images from wikimedia commons.

Testing Skype

Use a tone generator software (tonegen is free but 'expires' to test the frequency response range of skype (or your microphone).

Noise and decibels (dB)

Noise is unwanted sound.

Sound level is measured in decibels (dB).

http://impact.books.officelive.com/ProtectYourHearing.aspx

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/toyota-to-fit-active-noise-cancelling-to-crown-hybrid

The Speed of Sound

Sound is a longitudinal wave.

Try out the following simulations:
http://www.kettering.edu/physics/drussell/Demos/waves/wavemotion.html

http://www.phy.hk/wiki/englishhtm/Lwave.htm

http://www.cbu.edu/~jvarrian/applets/waves1/lontra_g.htm

Sound can travel in many different media. Which properties of the medium will determine the speed of sound in it?

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).

IGCSE June 2008 Question 2

The number of waves per second.pitch

dolphindolphin

http://commons.wikimedia.org/wiki/File:Parc_Asterix_22.jpg

http://commons.wikimedia.org/wiki/File:Typical_diver_charted.jpg

The Sound of Music

http://upload.wikimedia.org/wikipedia/commons/2/22/Octaaf0320w.JPG

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.

Light

Light is an electromagnetic wave, therefore: It travels at a speed of light.

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

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

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

http://electricly.com/wp-content/uploads/2010/05/white-mono-chromeatic-Laser-diodes.png

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

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:
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_and_refraction.svg

i=r

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_plane_jpg.htm

Bookwork

Page 85 and 87.

The Dog at the Beach

It's probably not necessary to load the picture of the dog that was here :)

How the Dog Runs

Sea Sandhttp://commons.wikimedia.org/wiki/File:Dog_retrieving_stick.jpg

http://commons.wikimedia.org/wiki/File:2009-11-19_(31)_Branch,_Ast.JPG

http://commons.wikimedia.org/wiki/File:Brittany_Spaniel_Dog.jpg

How the Dog Runs

Sea Sand

http://commons.wikimedia.org/wiki/File:Dog_retrieving_stick.jpg

http://commons.wikimedia.org/wiki/File:2009-11-19_(31)_Branch,_Ast.JPG

http://commons.wikimedia.org/wiki/File:Brittany_Spaniel_Dog.jpg

Sand

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 down, and bends ____________ the normal.

As light enters a less dense medium, it speeds up, and bends ____________ from the normal.

http://www.daviddarling.info/images/refraction.gif

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

Why Something Looks Bent in Water

http://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Pencil_in_a_bowl_of_water.svg/1000px-Pencil_in_a_bowl_of_water.svg.png

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

Angles

The Semi-Circular Block

When light is shone towards the centre of the (semi) circle, the angle if incidence is always ________.

The Critical Angle is the angle for which the refracted ray has an angle of refraction of 90.

10A got to here just intro TIR and CA

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.

Determining The Critical Angle

Determine the critical angle for perspex.

While you are using the ray boxes, also observe and draw how light refracts through a rectangular perspex block, and the convex and concave lenses.

http://www.one-school.net/Malaysia/UniversityandCollege/SPM/revisioncard/physics/light/images/criticalangle.png

http://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/Total_internal_reflection_of_Chelonia_mydas_.jpg/800px-Total_internal_reflection_of_Chelonia_mydas_.jpg

Why Do Diamonds Sparkle

http://commons.wikimedia.org/wiki/File:CZ_brilliant.jpg

Questions

Page 89 & 91.

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.

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).

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.

C

F

F

Ray 1: Parallel to the principle axis and through the focus.

Ray 2: Through the optical centre.

Ray 3: Through the closest focus and then parallel to the principle axis.

principle axis

http://upload.wikimedia.org/wikipedia/commons/a/af/Pencil_drawing.png

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.

C

F

F

Ray 1: Parallel to the principle axis and through the focus.

Ray 2: Through the optical centre.

Ray 3: Through the closest focus and then parallel to the principle axis.

principle axis

Convex Lens Summary

object positionImage positionReal
/virtualEnlarged / Diminished / same sizeUpright / InvertedUse (if any)

Beyond COn CBetween C and FOn FBetween F and the Lens

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

CAMERA

F

At this point, the image of the man is focussed on the film.

Film/ CCD

CAMERA

F

When the man walks closer, the(larger) image forms behind the CCD.

Film/ CCD

CAMERA

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.

Film/ CCD

An Excellent Site to Try Out

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=48.msg297#msg297

In this simulation it's possible to try many different locations for objects and images.

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.

Images will always be _______, ______,and ________.

Concave lenses will not be examined in IGCSE exams.

http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/imggo/ccv.gif

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.

Parallel verses Non-Parallel Rays

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.

sun

DON'T FORGET ARROWS!!

Lenses in IGCSE

Only diagrams for convex lenses will be examined.

Answers