2. WAVES A wave carries consists of oscillations which move without carrying matter with them. The oscillations carry energy. The energy can be used to carry a signal.
3. Pulse A pulse is a single wave 'bump' or a “disturbance”. A pulse can easily be sent down a string or spring.
5. Wavelength = λ = lowercase (Greek) 'lambda'. What is the relationship between v, f and λ? http://www.science-class.net/Notes/Images_8th_Notes/Transverse-Wave.png Waves
7. 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. http://www.antonine-education.co.uk/Physics%20A%20level/Unit_2/Waves/Progressive_Waves/Trans_Long.htm
9. Example Stella 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?
10. Example 2 Avinarsh shouts across the room at Paul. 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 Avinarsh's voice?
11.
12. State and explain the wave equation, including explaining why it works.
13. 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 :)
14. 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 * 10 8 ) meters per second. Calculate the wavelength of red light, given that it has a frequency of 500 000 000 000 000 (5 * 10 14 ) Hertz.
15.
16. Hana 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 Hana notice the wave crests or troughs? B. How far apart are two crests or two troughs? Note for blog: This was not covered in class, but would be a good revision exercise.
17. Quantity Symbol Formula Unit Speed/ velocity V s = f* λ metres per second (m/s) f = v/ λ Hertz (Hz) λ (lambda)
21. We can also draw them as a line through the middle of the wave, often called a ray .
22. What is the mathematical relationship between the ray and the wavefronts?
23.
24. At a boundary a wave can reflect. http://science.jburroughs.org/mschober/waveslite/problem6solution.html
25.
26. A change in speed causes a change in direction.
27. Depth of water changes the speed of waves. Image from Giancoli Physics, Sixth Edition. Please ask me if you would like to see the book it came from.
30. The diffraction is generally only noticeable if the gap is not much larger than one wavelength. http://innovativescience.blogspot.com/2011/02/diffraction.html
31.
32. All EM Waves A. Are transverse B. Can travel through a vacuum C. Travel at c, 3*10 8 m/s
37. Electromagnetic Spectrum Wave Approximate Frequency Approximate Wavelength Uses Radio waves 10 3 m Microwaves 10 -2 m Infra Red Waves 10 -5 m Visible Light 5 *10 -7 m Ultraviolet Light 10 -8 m X Rays 10 -10 m Gamma Rays 10 -12 m 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
38. 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
39.
40. A continuous variation is called an analogue 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
41.
42. Either the frequency or amplitude must be changed (modulation) to carry the signal. http://www.softwareforeducation.com/wikileki/index.php?title=FM
43.
44. Absorption by the Atmosphere http://en.wikipedia.org/wiki/File:Atmospheric_electromagnetic_opacity.svg
45.
46. 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
47.
48. FM signals are better quality, and are generally used in urban areas. http://scienceaid.co.uk/physics/waves/radio.html
67. 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,
74. Whistle = 10 000 Hz. All images from wikimedia commons.
75.
76.
77. Sound level is measured in decibels (dB). http://impact.books.officelive.com/ProtectYourHearing.aspx Decibels scale image
78.
79. 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 Antinoise image
80.
81. Try out the following simulations: http://www.kettering.edu/physics/drussell/Demos/waves/wavemotion.html
95. Note: this was only used for 10A on Tuesday 9/13 (fire drill); you will do the experiment and other slides next class.
96.
97.
98. However, most things which produce sound (especially musical instruments) produce other notes, called overtones, which make notes of the same frequency sound different.
99. If two notes are an octave apart, one has double the frequency of the other.
100.
101. Compare your result to the official value. Write a comparison – more? Less? Reasonable? Why might they be different?
114. The eye detects light (more later). Some things emit light (eg __________) while most things we see reflect light (eg _____________________) http://commons.wikimedia.org/wiki/File:Gluehbirne_2_db.jpg
115. 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
116.
117. 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:
122. 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
123.
124. Reflected rays follow three 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 θ i = θ r
125.
126. 1. the same size 2. the same distance from the mirror 3. laterally inverted (left and right swapped).
127. A great site below: http://www.kss.sd23.bc.ca/staff/jstracha/physics_11/course_material/unit8/U08L01/pages/ray7_plane_jpg.htm
128.
129. The Dog at the Beach http://www.flickr.com/photos/velo4it/1746214612/ (no need to load this URL unless you like pictures of dogs and/or the beach)
130. How the Dog Runs 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
131. How the Dog Runs 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
132.
133. As light enters a more dense medium, it slows down, and bends ____________ the normal.
134. As light enters a less dense medium, it speeds up, and bends ____________ from the normal. http://www.daviddarling.info/images/refraction.gif
135.
136. 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
137.
138. This is why a prism can separate white light into its different colours.
139. This process is known as dispersion. http://upload.wikimedia.org/wikipedia/commons/0/06/Prism_rainbow_schema.png
142. The Critical Angle is the angle for which the refracted ray has an angle of reflection of 90 °.
143.
144. 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.
145.
146. While you are using the ray boxes, also observe and draw how light refracts through a rectangular perspex block. http://www.one-school.net/Malaysia/UniversityandCollege/SPM/revisioncard/physics/light/images/criticalangle.png
148. Why Do Diamonds Sparkle http://commons.wikimedia.org/wiki/File:CZ_brilliant.jpg
149.
150. 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.
154. 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
155.
156.
157. Lens Calculations d o = distance from object to lens d i = distance from image to lens F = focal length C = centre of curvature = 2F
158. Convex Lens Summary object position Image position Real /virtual Enlarged / Diminished / same size Upright / Inverted Use (if any) Beyond C On C Between C and F On F Between F and the Lens
159. CAMERA Film/ CCD If the image were a very, very long way away, what would the distance from the lens to the film be?
164. Concave lenses will not be examined in IGCSE exams. http://en.wikipedia.org/wiki/File:Lens1b.svg This site explains lenses very well: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/imggo/ccv.gif
169. Parallel light rays converge at the __________. Objects nearby produce light rays which are not parallel. Light rays fro m an object of finite d o will meet at a distance d i . This distance can be found using a ray diagram or calculations. DON'T FORGET ARROWS!! sun