Introductory Physics, High School Learning Standards for a Full First-Year Course

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1 Introductory Physics, High School Learning Standards for a Full First-Year Course I. C ONTENT S TANDARDS 4.1 Describe the measurable properties of waves (velocity, frequency, wavelength, amplitude, period) and explain the relationships among them. Recognize examples of simple harmonic motion. 4.2 Distinguish between mechanical and electromagnetic waves. 4.3 Distinguish between the two types of mechanical waves, transverse and longitudinal. 4.4 Describe qualitatively the basic principles of reflection and refraction of waves. 4.5 Recognize that mechanical waves generally move faster through a solid than through a liquid and faster through a liquid than through a gas. 4.6 Describe the apparent change in frequency of waves due to the motion of a source or a receiver (the Doppler effect). 6. Electromagnetic Radiation Central Concept: Oscillating electric or magnetic fields can generate electromagnetic waves over a wide spectrum. 6.1 Recognize that electromagnetic waves are transverse waves and travel at the speed of light through a vacuum. 6.2 Describe the electromagnetic spectrum in terms of frequency and wavelength, and identify the locations of radio waves, microwaves, infrared radiation, visible light (red, orange, yellow, green, blue, indigo, and violet), ultraviolet rays, x-rays, and gamma rays on the spectrum.

2 1. Which of the following is the best example 2. People perceive sound differently in air than of a wave? they do under water. Which of the following A. a stone rolling downhill correctly compares the motion of sound waves B. a vehicle traveling on a bumpy road in air and in water? C. a string vibrating on a guitar A. Sound waves travel faster in air than in D. a grasshopper jumping up and down water. occasionally. B. Sound waves travel slower in air than in water. C. Sound waves travel in air but do not travel in water. D. Sound waves travel at the same speed in air and in water. C. a string vibrating on a guitar. A vibrating guitar string is a wiggle in space and time that repeats regularly. The matter in the guitar string does not move from one placed to the other, but the energy does. B. Sound waves travel slower in air than in water. Air molecules are further apart than water molecules. The wave will propagate faster through a denser The diagram below shows what happens when a particular light wave strikes a boundary.

3 3. The illustration below shows three toy ducks floating on water, moving up and down as a wave travels to the right with a velocity of 3 m/s. 4. A student is sitting in a large stadium far away from the starting line of a footrace, while listening to the footrace on the radio. As the race starts, the student hears the sound of the starting pistol on the radio. Shortly after that, the student hears the sound of the starting pistol from inside the stadium. Which of the following is the frequency of the wave? A Hz B Hz C. 1.5 Hz D. 6.0 Hz Which of the following best explains these observations? A. Mechanical waves travel faster than electromagnetic waves. B. Electromagnetic waves travel faster than mechanical waves. C. The radio's signal traveled a shorter distance than the sound wave traveled. D. The radio s microphone was farther away from the starting line than the student was. A Hz v = f" f = v " f = 3 m/s 4 m f = 0.75 Hz B. Electromagnetic waves travel faster than mechanical waves. The sound of the starting pistol travels as an electromagnetic wave from the microphone to the radio speaker, and as a mechanical wave from the source to your ear. Electromagnetic waves travel at the speed of light through a vacuum, always faster than mechanical waves.

4 5. What is the frequency of ocean waves that have a speed of 18 m/s and a wavelength of 50 m? A Hz B Hz C. 2.8 Hz D. 9.0 Hz 6. A student standing on the edge of a swimming pool sees a painted mark on the bottom of the pool. The mark appears to be at a shallower depth than the actual depth of the pool. Which of the following descriptions of light waves best explains this observation? A. Light from the mark travels through the water in a curved path. B. Light from the mark is refracted as it travels from the water to the air. C. Light from the mark is reflected as it travels from the water to the air. D. Light from the mark bounces off the boundary between the water and the air. B Hz v = f" f = v " 18 m/s f = 50 m f = 0.36 Hz B. Light from the mark is refracted as it travels from the water to the air. Light crossing a boundary between two media will change its direction (if the speed of light is different in the two media). This property is called refraction.

5 7. An organ pipe produces a musical note with 8. Which of the following statements applies to a wavelength of 2.72 m. What is the frequency a longitudinal wave? of this note if the speed of sound is 348 m/s? A. The motion of the medium is random. A Hz B. The motion of the medium is in a circular B. 128 Hz pattern. C. 260 Hz C. The motion of the medium is parallel to D. 466 Hz the motion of the wave. D. The motion of the medium is perpendicular to the motion of the wave. B. 128 Hz v = f" f = v " 348 m/s f = 2.72 m f =128 Hz C. The motion of the medium is parallel to the motion of the wave. A longitudinal wave is defined as a wave in which the motion of the medium is parallel to the motion of the wave.

6 9. Five bowling balls are lined up touching one 10. A sound wave can be transmitted through another on a smooth surface. Striking the first all of the following except ball with a hammer makes the fifth ball move A. a gas. away from the group. The force of the hammer B. a liquid. was transmitted through the line of balls as C. a solid. what type of wave? D. a vacuum. A. electromagnetic B. heat C. longitudinal D. transverse C. Longitudinal. The wave energy is traveling parallel to the direction of the pulse. D. a vacuum. Sound is a mechanical wave, it requires a medium to be transmitted.

7 6. Electromagnetic Radiation Central Concept: Oscillating electric or magnetic fields can generate electromagnetic waves over a wide spectrum. 11. Sound reaches our ears because sound makes air particles A. heat up. B. cool down. C. slow down. D. vibrate. 12. The figure below shows regions of the electromagnetic spectrum. D. Vibrate. The vibration of air particles causes the vibration of the parts of our ears which send a signal to our brain which we perceive as sound. Which of the following waves has the highest frequency? A. visible light B. microwaves C. ultraviolet rays D. infrared radiation C. Ultraviolet rays have higher frequencies than visible light. Visible light has a higher frequency than infrared, and infrared has a higher frequency than microwaves.

8 13.) Each of the following illustrations shows the movement of a 1 kg object. Which of these is an example of simple harmonic motion? B. Simple harmonic motion is an oscillation, a repeated back and forth movement. Correct Answer and Explanation

9 6. Electromagnetic Radiation Central Concept: Oscillating electric or magnetic fields can generate electromagnetic waves over a wide spectrum. 14. Which of the following describes how a microwave oven heats food? A. The oven s interior reflects heat onto the food. B. The oven s interior, like a lens, focuses heat onto the food. C. Water molecules in the food reflect energy from microwave radiation. D. Water molecules in the food absorb the energy of microwave radiation. 15. Which of the following is designed to transform an electromagnetic wave into a mechanical wave? A. a portable radio B. a television screen C. a computer monitor D. a mercury thermometer D. Water molecules in the food absorb the energy of microwave radiation. The wave frequency generated by microwave ovens causes water molecules to absorb energy and vibrate. This increase in kinetic energy of the water molecules is an increase in temperature. The heat from the water molecules can then be transferred (by conduction) to other kinds of molecules in the food. A. A portable radio. Radio signals are carried on electromagnetic radio waves. In a radio, that wave energy is transferred to the vibration of a speaker, which sets up mechanical waves (sound waves, to be specific) through the air. Television screens and computer monitors produce electromagnetic waves (visible light). Thermometers do not really use either type of wave.

10 6. Electromagnetic Radiation Central Concept: Oscillating electric or magnetic fields can generate electromagnetic waves over a wide spectrum. 16. Which of the following devices relies on electromagnetic radiation in the radio wave region of the spectrum for operation? A. sun tanning lamp B. electric light bulb C. cellular telephone D. electric toaster 17. Visible light passes through glass. Other types of electromagnetic radiation are able to pass through other materials in a similar way. Which of the following are used in medical technology because they can pass through some parts of the human body? A. x-rays B. infrared waves Comet C. microwaves D. ultraviolet rays C. Cellular telephone signals are transmitted at frequencies in the radio (and microwave) portion of the electromagnetic spectrum. A. X-rays can penetrate the soft tissues of the human body, but cannot travel through teeth and bones. Tanning lamps produce mostly UV and some visible radiation. Light bulbs produce mostly visible and some IR radiation. Toasters produce mostly IR and some visible radiation.

11 Practice: Open-response question #1 BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION. Show all your work (diagrams, tables, or computations) If you do the work in your head, explain in writing how you did the work. The electromagnetic spectrum is shown below. There are multiple stages involved in the transmission, reception, and display of a television broadcast. A signal is sent by satellite from the station and relayed to the television by several methods. The signal is translated electronically and converted into an image on regular, liquid crystal, or plasma TV displays. The viewer then sees the image. a. Identify one region of the electromagnetic spectrum used by television and explain how it is used. b. Select a different portion of the electromagnetic spectrum that is not used by television. Explain a useful application of this spectral region. Answer: The radio section of the electromagnetic spectrum is used in television broadcasts. The transmitter at the TV station sends out a signal as a series of radio waves that carry the information to individual TV s. OR The visible section of the electromagnetic spectrum is used by televisions. The television produces a visible image that consists of different wavelengths of visible light. Different wavelengths are visible as different colors. b. Select a different portion of the electromagnetic spectrum that is not used by television. Explain a useful application of this spectral region. Microwaves are not used by TV. One useful application of microwaves is the microwave oven, which shines microwaves on food. The water molecules in the food absorb the microwaves and heat up. OR Infrared waves are not (really) used by TV. (It is true that most TV s get hot, so they will emit IR radiation to their surroundings. However, this is not really using IR waves). A useful application of IR waves is in heat lamps. Heat lamps emit IR

12 radiation that can be absorbed by food placed under them. This keeps the food warm. IR waves are also often used in remote controls. The remote control produces a signal that is transmitted to the television (or other device) via IR waves. OR Ultraviolet waves are not used by television. UV rays can be used to sterilize (kill bacteria on) things. Often, you will find UV rays in restaurant kitchens for employees to sterilize their hands. Some labs will have cabinets where UV rays sterilize safety goggles. Biology labs use UV lights to sterilize surfaces and prevent contamination of cells and organisms grown in the lab. OR X-rays are not used by television. X-rays can be used for medical purposes. Since they pass through soft tissues of the human body but not through bones, X-rays can be used to produce images of the bones and teeth. OR Gamma rays are not used by television. Gamma rays can be used in the treatment of cancer. The gamma rays can be aimed at a tumor, killing the cancerous cells.

13 Practice: Open-response question #2 BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION. Show all your work (diagrams, tables, or computations) If you do the work in your head, explain in writing how you did the work. What happens when light wave strikes a boundary? a. Identify each light ray, A, B, and C, as an incident, a refracted, or a reflected ray. b. Describe the relationship between angles x1 and x2. c. Describe how this setup could be changed so that the size of angle x3 is different.medium (liquid) than through a less dense medium (gas) Answer A. Ray A is the incident ray, B is the reflected ray, and C is the refracting ray. B. Angles x 1 and x 2 are equal. The angle of incidence is equal to the angle of reflection. C. The angle x 3 depends on what materials are on the two sides of the boundary. In the picture, x 3 is smaller than x 1, which indicates that the light moves faster in Medium 2 than it does in Medium 1. To change the angle, you could change either medium in which light travels with a different speed.