4Wave-3
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Contents
Outcomes
- Pupils can recall the hearing range of a human and determine whether a frequency lies within the range and understand that
- Pupils understand that any sound wave with a frequency greater than 20kHz is known as ultrasound.
- Pupils can recall different uses of ultrasound and can explain the idea of ultrasound scanning using an echo.
- Pupils can describe how to measure the speed of sound using a clapping method and an electronic method.
Specification References
- 3.26 recall that sound waves are longitudinal waves which can be reflected, refracted (and diffracted SA only)
- 3.27 recall that the frequency range for human hearing is 20 Hz – 20 000 Hz
- 3.28 describe how to measure the speed of sound in air
Starter
- Carry out pupil hearing range experiment using speaker and signal generator. Pupils will probably bring up the The Mosquito at this point.
Main Body of Lesson
- Move onto reviewing (or starting) the two equations needed for this section (v=f and T=1/f) you may just quicly want to flag up the regular speed equation (s=d/t) as they often forget that this applies too.
- Discuss the nature of ultrasonic sound.
- Discuss the uses of ultrasound in diagnostic sonography, therapeutic medicine, industrial nondestructive testing and cleaning. Why not bring in some jewellery and clean it in the lesson.
- Demonstrate nature of sound waves. AGR has great videos.
- There are lots of animations here
- Show pupils the speed of sound in solids, liquids and gases (set a large value for distance (≈50000m)).
- Demonstrate how to find the speed of sound using the "clapper" method.
- Demonstrate that sound waves cannot travel through a vacuum.
- Pupils will probably ask about shattering a glass with sound.
Plenary
- Link frequency and amplitude to sound waves using audio clips.
Homework
Additional Information
Resources Required
- Signal Generator
- Speaker
- Vacuum pump connected to Bell Jar
- Ultrasonic cleaner
Textbook References
- Pople 6.03 pp. 128-135
Website References
Skills Addressed
Safety/Hazards
- The main risk is from the vacuum pump and apparatus. The specific risk assessment must be read before using the apparatus.