AQA GCSE Changes in Sound Waves (Physics)
Sound Waves
A sound wave is a longitudinal wave, so they vibrate along the direction in which they transfer energy.
Physical State of Medium and Speed of Sound Waves
Sound waves will travel fastest through solids, slowest through gases. This is shown by the bar chart below.
Speed of Sound in air and Temperature.
As the air temperature increases, so does the speed of sound.
| Temperature (oC) | Speed of Sound (m/s) |
|---|---|
| 0 | 331 |
| 10 | 337 |
| 20 | 343 |
| 30 | 349 |
This is because at higher temperatures the air molecules have more kinetic energy, so they move faster. This means they transmit the sound waves quicker.
Changes in Sound Waves
When sound waves travel from one medium to another (e.g., from air to water or from water to steel), their velocity, frequency, and wavelength are related by the wave equation:
Wave speed, v = Frequency,f x Wavelength,λ
If the sound wave moves across a boundary from one medium to another and both the speed and direction change, then the wave will be refracted.
Less dense medium to a more dense medium.
If a sound wave moves from air(less dense) to water (more dense) medium.
Velocity (wave speed) and wavelength both increase!
Frequency is constant
If the wave enters at an angle, it bends towards the normal because sound travels faster in water.
More dense medium to a Less dense medium.
If a sound wave moves from water (more dense) medium to air(less dense).
Velocity (wave speed) and wavelength both decrease!
Frequency is constant
If the wave enters at an angle, it bends away from the normal because sound travels slower in air.
Practice Question
1.Is sound a transverse or longitudinal wave?
2.A sound wave passes through each of the following materials: Copper, oil and nitrogen gas.
2a. Which material will the sound wave travel through fastest?
2b. Which material will the sound wave travel through slowest?
3. Why does sound travel faster through the air in the summer compared to the winter?
4. For refraction of a sound wave to occur, which properties of the sound wave need to change?
5. If a sound wave moves from water to steel, how would you expect its velocity, wavelenth and freqency to change?
Absorption and Emission of EM Radiation
JJ Thomson and Plum pudding model
Ernest Rutherford and the Nuclear Model
Niels Bohr changing the Nuclear Model
Discovering the Proton and Neutron
Measuring radiation from radioactivity
Radiation types and properties
Random nature of radioactive decay
Radioactive contamination or irradiation
Hazards of contamination and irradiation
Studies on the effects of radiation on humans
Different half lives of radioactive isotopes
Nuclear Fission Chain Reaction
Writing nuclear fission equations
Accordion Content
Accordion Content