Yes, We're Still on Waves

Intro Physics conducted a lab investigation on sound waves, looking at properties of sound for tuning forks, the human voice, an automated tone dialer and musical instruments.  We contrasted pure tones, with tones accompanied by overtones.  A tuning fork struck softly vibrates with a sole, fundamental frequency, but one that is struck sharply produces overtones simultaneously with the fundamental tone.  The human voice produces a variable number of overtones with the fundamental frequency and that gives each voice its characteristic sound.  The same is true for musical instruments.  Two instruments playing the same note do not sound the same due to the numbers and intensities of overtones produced by each instrument.  For the tone dialer, it was seen that the phone company assigns each number a row and column frequency to indicate its position on the matrix.  We will talk about this lab on Monday and then spend more time with sound intensity.

Physics D, F and Honors Physics started work on wave interference and diffraction today.  We discussed the conditions required to observe interference of light and how those conditions could be and were met to demonstrate light interference as part of the evidence package that light was actually a wave.  Folks saw laser light interference and the dark/light fringes characteristic of light interference and we then looked at how to calculate the position of those fringes.  On Monday, we'll add diffraction to the discussion, which helps to explain how Young's double-slit experiment was able to document light interference.

A Day of Tests

Physics D, F and Honors Physics took their Refraction exam today and move onto Diffraction and Interference tomorrow. Intro Physics went over their Waves exam and then moved onto an exploration of sound. We reviewed the basic nature of sound waves as longitudinal, mechanical waves, factors that affected the speed of mechanical waves and then turned attention to loudness. We linked loudness with the amplitude of a sound wave and then approached the idea from the perspective of intensity, both absolute and relative. We looked at the intensity formula, which we'll practice with tomorrow, and then began to discuss the logarithmic nature of the ear's perception of sound and how that was incorporated into the decibel scale. Tomorrow, we finish with loudness, look at the range of hearing/vocalization of sounds of humans and other organisms and get a little math practice with intensity.

Exams and Their Preparation

Intro Physics took their Waves test today and will move on to the specifics of sound and light tomorrow. Physics F and Honors Physics went over their lab work on lenses and image formation before moving into reviewing for their exam tomorrow. Physics D conducted their lab work, with their review having been completed yesterday. After tomorrow's round of exams, the upper-division physics folks move onto a quick look into diffraction and interference before turning towards electricity.

Simulation

Here's a little simulation for image formation by a converging lens. Check the 'virtual image' box to have the program include those as options and 'principal rays' to show the types of rays you used to construct ray diagrams.

Starting Some Review

Physics D and Intro Physics took the period to go over last night's homework and review for their upcoming exams (Thursday for Physics D and tomorrow for Intro Physics). Physics F and Honors Physics will have their review tomorrow and took today to complete their lenses labs. Make sure you are aware of patterns of image formation by convergent and divergent lenses, the definition of depth of field and how depth of field, aperture and shutter speed relate in the field of photography. Physics D will work on these labs tomorrow, probably only the convergent/divergent lens lab and all upper division physics folks take their refraction exam on Thursday.

Lenses

Physics D did not meet due to an assembly, so will only conduct one investigation of their lab unit before Thursday's test. Physics F and Honors Physics started their labs today, beginning with lenses and image formation and moving on to aperture and depth of field. Depending on the time allotted groups made it to different stopping points and will continue with their work tomorrow. Most groups, at minimum, worked through real image formation by double-convex lenses and saw clearly the pattern demonstrated in the table in their textbooks that we referenced during lecture, but by tomorrow at the end of the period, all groups should be finished with both experiments and ready for Wednesday's review in preparation for Thursday's exam.

Intro Physics took on the topic of standing waves today, and used their lab on this topic to highlight their work. We discussed the physical structure of standing waves,the interaction of reflection and interference that forms them and relationship between frequency and wavelength for standing waves and saw how it met the pattern for other wave types, as wavelength decreased through the standing wave series, the frequency increased to keep the speed of the waves constant in the medium. We looked at how to calculate wavelength for standing waves and use wavelength, along with the wave speed formula to assess the frequency of the standing waves. We then noted that the relationship between the frequency of standing waves in a series and saw they were integral multiples of each other. In the next chapter, we'll examine standing waves in more detail when we discuss music and harmonic series. Tomorrow, we review tonight's homework, the chapter concepts and answer questions in preparation for Wednesday's exam.

Light and Waves

Intro Physics continued their discussion of wave interactions with a discussion of refraction and interference. We discussed when refraction would occur, described how the path of travel change when a wave enters a particular material and then moved to both constructive and destructive wave interference, along with the formation beats. On Monday, we'll discuss standing waves, Tuesday is review day and Wednesday is exam day. On Thursday, we begin a specific examination of sound.

Physics D, F and Honors Physics reviewed their work with lenses, then turned attention to optical phenomena such as total internal reflection, mirage formation and dispersion. We looked at examples of natural and man-made fiber optics, then examined how mirages are formed due to atmospheric refraction and dispersion, along with it's relationship to rainbow formation. On Monday, Physics D will review for their upcoming exam (Thursday), while F and Honors Physics begin work on two lab activities for image formation by lenses and the relationship between aperture and depth of field. D Block will start on these labs Tuesday.

Lenses!

Physics D, F and Honors Physics worked with the mathematics of thin lenses today. We reviewed the relevant formulas, which we had used in the last chapter for mirrors, and the sign conventions for lenses before folks were turned loose to work problems, draw ray diagrams and answer their questions independently. Tomorrow, we move onto refractive phenomena such as mirages, total internal reflection and dispersion.

Intro Physics reviewed their labs of wave properties, then took a moment to review reflection before moving on to diffraction, the ability of waves to spread around the edges of an object or through an opening in the object, like a door. We discussed examples of diffraction and touched on refraction before the bell. Tomorrow, we take on refraction and interference.

Waves and More Waves

Physics D, F and Honors Physics continued on with light and refraction today by looking at lenses. We completed light and reflection last week and, after Monday's exam we turned towards refraction, the change of path of light due to traveling a different speed in a new medium. Yesterday, we defined refraction, discussed when refraction did and did not occur, defined the index of refraction and discussed how the values could be used to assess properties of a substance in terms of the behavior of light and used Snell's Law to evaluate the exact path of travel of light in a material. Today, we took on lenses and began to discuss properties of lenses, contrast diverging and converging lenses and take a look at ray diagrams for lenses. Tomorrow, we'll continue on this with this and get some practice with the math involving lenses.

Intro Physics continues with waves and wave behaviors and, today and yesterday, worked on lab work concerning wave features, wave reflection and interference. We used springs to model transverse and longitudinal waves, set up standing waves in a rope and used a microphone and the Vernier system to examine sound waves and the phenomenon of beats. Tomorrow, we'll discuss these labs and continue beyond reflection to other wave behaviors, such as refraction and diffraction.

Waves and Optics

Intro Physics worked on a lab targeting energy conservation in simple harmonic motion. We let a spring oscillate, after experimentally determining the spring constant, and saw the pattern conform nicely to a sine curve. Looking at the graphs of kinetic energy and elastic potential energy, it was seen that they were inverse of each other and, at any point, the sum of the two energies was about the same value as any other point in the motion. We then added a large coffee filter to the bottom of the spring's mass and saw how mechanical energy was no longer conserved in the presence of significant frictional resistance. Tomorrow, we'll dig further into waves and wave features.

Honors Physics, Physics D and Physics F worked on practice problems for curved mirrors. Folks had to use the mirror formula as well as the two versions of the magnification formulas to solve problems involving image properties, object properties or mirror properties. Most people realized that reading the problem carefully and using the information to correctly assign signs for values was a critical skill for success. Physics D and F also had to draw ray diagrams for concave mirrors, while Honors Physics had to the same for both types of mirrors. We'll go over these problems tomorrow before moving on to color and polarization.

Riding the Waves

Intro Physics moved into the area of vibrations and waves today, with an overview of the nature of waves, the difference between mechanical and electromagnetic waves and how waves relate to vibrations. We dipped our toes into a specific type of vibration, that which is described by simple harmonic motion and Monday's lab will allow folks to examine a system exhibiting simple harmonic motion (an oscillating spring), measure the spring force (which is the restoring force of the system) and how energy is conserved in the motion.

Physics D completed their lab work with curved mirrors and will discuss that lab on Monday. Honors Physics discussed their lab today and continued to discuss properties of image formation by curved mirrors. Physics F did the same and had time to work a couple of practice problems for mirrors. On Monday, time will be given for people to practice using the mirror equation and magnification equations for both concave and convex mirrors, as well as draw ray diagrams. The test that is currently scheduled for Wednesday will likely get moved to Thursday, but we'll decide for certain on Monday.

Mirrors and Reflection

Intro Physics took their heat, temperature and phase change exam today and move on tomorrow to vibrations and waves.

Honors Physics, tiny class that it was, completed their curved mirrors lab and Physics D started the same lab during the long block. Both concave and convex mirrors were examined and patterns of image formation by these mirrors were investigated. Concave can make both real and virtual images and we looked at how the position of the object with respect to the mirror affected the properties of the real image that was formed. Convex can only make virtual images and we used the parallax method to determine image location. Tomorrow, D Block will complete the lab and Honors Physics will discuss the lab as part of the discussion about mirrors and the mirror equation.

Physics F discussed their mirrors lab and looked at how the data collected in lab related to the mirror equation we are using in class. We then took time to begin discussing the properties of concave mirrors and how those mirrors made images. We'll continue with this tomorrow and add on convex lenses, along with the use of ray diagrams to determine image position and properties.

Energy, Be it Heat or Light

Intro Physics worked with latent heat and phase change today in class. We discussed phase changes and phase-change diagrams, then looked at how to calculate the amount of energy required to change the phase of a substance - latent heat. We discussed why latent heat of vaporization was greater than latent heat of fusion and worked through an example where folks had to calculate the energy required to heat a substance, change its phase, then continue to heat it to a final temperature. We'll go over the homework problems in class tomorrow before beginning to review for Thursday's exam.

Physics D and Honors Physics began to work on the area of spherical mirrors today in class. We looked at the the types of curved mirrors (concave and convex), the nature of radius of curvature and focal length and started to examine how these types of mirrors formed images. We'll continue with this tomorrow for D Block and Honors Physics will work on a lab that will focus on image formation and the formula we introduced today in class. Physics F conducted this lab today, looking at images formed both by concave and convex mirrors. Concave mirrors form both real and virtual images, depending on placement of the object, but convex mirrors only form virtual images. We'll start discussing the details of image formation tomorrow in class, and review our lab as part of the class discussion.

Moving On To Light

Physics D, F and Honors Physics began their discussion of light today with an overview of the nature of light as a transverse, electromagnetic wave (when it behaves as a wave), the members of the EM spectrum and their uses, the speed of light and how Huygens viewed light waves and their propagation. Physics D and Honors Physics also looked at light intensity, but Physics F will get there on Monday, when they will also start, with the other sections, on an examination of reflection and reflection by flat mirrors.

Intro Physics discussed yesterday's lab investigation on phases and phase change before turning attention towards the liquid and gas phases of matter. We continued to describe matter in terms of energy, particle motion, volume and shape and saw how the pattern of increasing energy took solids to liquids and then gases. We'll hit plasma on Monday and then begin our look at phase changes, phase change diagrams and latent heat.

Saying Farewell to Sound

Physics D, F and Honors Physics took their Sound exams today and begin with light and reflection tomorrow. Intro Physics conducted a lab investigation on phase changes. We began talking about phases of matter yesterday and today, examined water undergoing the liquid-solid phase changes. We charted the temperature change of freezing water and melting ice and overlaid the graphs to see that the solid-liquid change (melting) occurred at the same temperate as the liquid-solid transformation (freezing) and that the temperature did not change during the process of changing phase. We'll discuss the lab in class tomorrow as we continue looking at phases of matter and latent heat.

Swamped with Sound

Physics D and Honors Physics discussed the concepts of timbre and beats today in class. We used our work with harmonics to discuss the musical quality of sound and why different instruments, playing the same note, sound quite differently due to the numbers and intensities of harmonics each instrument produces. We then turned attention to beats, which is an interference phenomenon where two waves of similar frequencies produce a resultant wave with alternating soft (destructive) and loud (constructive) regions. The numbers of beats/second, or beat frequency equals the frequency difference between the incident waves. Tomorrow we review and Thursday is our exam, so come to class tomorrow with questions.

Physics D conducted two lab investigations, one that centered on sound production and beats and the other on standing waves. Students compared properties of waves produced by two different tuning forks struck separately and when they were struck simultaneously. The interference of the waves produced beats with, when the frequency was calculated, was equal to the frequency difference between the two tuning forks. Folks then generated standing waves on a string and measured properties such as wavelength, frequency and wave speed. As wavelength decreased, frequency increased so that the speed of the wave in the rope remained constant. We'll discuss this lab tomorrow, along with the idea of timbre and beats before reviewing for Thursday's exam.

Intro Physics discussed the relationship between work and heat. We looked at how doing work on a system can raise its internal energy and temperature and how a system doing work can experience a decrease in internal energy and temperature. We touched on the concept of thermodynamics and discussed how heat, work and internal energy are related in both heat engines and refrigeration systems. Tomorrow, we begin on phases of matter and phase chnge.

And We're Back

Intro Physics reviewed their work with specific heat, calorimetry and conservation of energy, before getting some practice solving problems involving heat transfer between objects. If we can assume some degree of conservation of energy, we can assume that the heat lost by one object equals the heat gained by a second and use that relationship to solve for specific heat of one substance, temperature change (initial or final or final temperatures, too) or mass. We'll go over these problems tomorrow before turning attention to phase change and latent heat.

Physics D and F discussed the concept of harmonics and the harmonic series produced by stringed instruments, pipes open at both ends and pipes closed at one end. We examined how the instrument types formed standing waves and why pipes closed at one end are different than the other two instrument types. The homework problems will give you practice calculating harmonic series for these instrument types and tomorrow, we use harmonics to discuss the concept of timbre before turning attention to beats and beat frequency.

Honors Physics worked on two lab investigations in class today, one focusing on beats and beat frequency and the second on standing wave formation. Beats are produced by interference of two waves of similar frequencies and the number of beats per second (beat frequency) is equal to the frequency difference between the two notes, and the data we collected in lab verified this relationship. The more difficult of the two investigations involved forming standing waves, which only form a certain frequencies in the medium. It took folks awhile to get the waves formed and stabilized long enough to collect data, which demonstrated that as wavelength decreased, frequency increased and by a predictable value. We'll talk about he labs tomorrow, as well as the harmonic series problems that were assigned, in class tomorrow before turning attention to timbre and beats.

Facing Vacation

The snow day yesterday will push Physics D, F and Honors Physics exams back one day, so they'll be the Thursday of the week we return from vacation. Between yesterday and today, these blocks moved forward with their study of sound. We looked at sound intensity, relative intensity and the decibel scale, structure and function of the human ear and how intensity and frequency play into human ability to hear. Today, Physics F worked with a lab centering on sound production by natural and artificial sources, how multiple waves are analyzed by the principle of superposition and how telephone companies code information in touch-tone systems, while Honors Physics moved forward into harmonic series and standing waves. Make sure you can properly calculate harmonic series for vibrating strings, pipes open at both ends or pipes closed at one end, in addition to determining wavelengths of standing waves based on the length of the vibrating string or air column.

Intro Physics built on their work with heat transfer by discussing the third method of heat transfer, radiation, and looking at examples of how heat is transferred as an energy wave. We then turned attention to specific heat and calorimetry. We defined specific heat and discussed how that property explains why some materials change temperature readily and others resist temperature change. We then looked at calorimetry and how a calorimeter uses the Law of Conservation of Energy to determine the specific heat of a material or the energy content of a fuel or food. When we return, we'll practice with specific heat and using the idea of energy conservation to solve problems involving heat transfer.

Have a good vacation!

Lots of Sound

Physics D discussed their lab investigation on properties of sound before exploring those properties more fully in class. We refreshed ourselves on the basics of sound, and added in additional descriptors and phenomena demonstrated by sound, such as pitch and the Doppler Effect. Physics F and Honors Physics built from this discussion, in which they engaged yesterday, to look at sound intensity, the decibel scale and sound and human health. We examined the formula for sound intensity and related that to relatively intensity and the decibel scale, before relating the decibel scale to human activities. Tomorrow, we look at features of the human ear and then start to broach the concept of harmonics and overtones.

Intro Physics worked on two lab investigations surrounding the concept of heat transfer. We looked at heat transfer between substances at different temperatures and when one substances was undergoing a phase change. By comparing heat lost to heat gained we were able to see conservation of energy in action, though we worked to minimize loss to the environment through the design and construction of a more efficient calorimeter. We'll discuss these investigations tomorrow in class, before taking on methods of heat transfer - conduction, convection and radiation.

A Nice New Monday

Intro Physics built upon Friday's discussion of temperature to examine the three major temperature scales (Celsius, Fahrenheit, Kelvin) and then practice converting between one scale and another. We then looked at the idea of heat transfer, focusing on the direction of spontaneous heat flow and how our nerves perceive that flow. We put a specific definition to heat energy and, in lab tomorrow, will look at heat transfer between two materials at different temperatures, as well as between materials where one is undergoing a phase change. Our last bit of discussion concerned thermal equilibrium and that is another concept tomorrow's labs will highlight.

Physics D completed their lab investigation into sound. Most groups worked with the tone dialer software to determine how telephone systems use sounds to encode information. Honors Physics discussed this lab in class today, along with the extra investigation about the mathematics of music before moving on (along with Physics F) to a discussion of sound wave properties, sound propagation, spherical waves, pitch and the Doppler Effect. Tomorrow, Physics D has this discussion and the other two blocks will take a look at sound intensity and resonance.