Heat, Temperature, Sound, and Wave Motion
Heat and Temperature
Heat is a physical magnitude that measures the energy transmitted from one body to another, reflecting the difference between their components. The unit in the International System of Units (SI) is the Joule (J). 1 calorie = 4.18 J.
Temperature: The temperature of a body depends on the kinetic energy of its particles (atoms, ions, or molecules).
Heat energy can be transmitted from one body to another in three ways: conduction, convection, and radiation.
- The propagation of heat by conduction takes place in solid bodies.
- Convection heat propagation is unique to fluids (liquids and gases).
Thermometer: These devices allow us to measure temperatures. There are three types: mercury, alcohol, and electronic.
Expansion: The increasing size of an object (solid, liquid, or gas) with increasing temperature.
- Liquids: Take longer for the same temperature increase and the same volume.
- Gases: Expand much more than solids and liquids for the same temperature increase and the same volume.
Celsius (Centigrade) Scale
The fixed points are 0°C to 100°C.
Differences Between Conduction and Convection
Convection is characteristic of fluids: it is accompanied by a displacement field and is produced by currents within the fluid. In contrast, in the propagation of heat by conduction, characteristic of solids, the solid particles in contact with the heat source acquire a high kinetic energy.
Wave Motion and Sound
The swaying motion of a body is called oscillatory motion. If oscillations are radiated, they are called vibrations.
Wave Motion is the propagation of an oscillatory motion through a medium.
Frequency: Number of oscillations made in the proper time. In the SI, frequency is measured in hertz (Hz).
Sound: A vibration transmitted as wave motion through matter. For this reason, sound cannot propagate in a vacuum.
- In homogeneous media, sound waves propagate at a constant speed. The speed of sound in air is 340 m/s.
- Sound propagates faster in solids than in liquids, and faster in liquids than in gases.
Qualities of Sound
The qualities of sound are intensity, pitch, and timbre.
- Intensity: The sound quality that allows us to distinguish it as strong or weak.
- Pitch: The sound quality that allows us to identify it as sharp or as serious.
- Timbre: The quality of sound that allows us to distinguish two sounds of equal intensity and pitch.
The normal human ear perceives sounds with frequencies between 20 Hz and 20,000 Hz.
- Sounds with frequencies above 20,000 Hz are called ultrasounds.
- Sounds with frequencies below 20 Hz are called infrasounds.
Ultrasound has many practical applications in medicine, knowledge of undersea features, and the sterilization of food, among others.
Echo and Reverberation
Echo: Produced when the sound we emit is reflected on a surface and returns to us, and we can distinguish it as a different sound. When it is indistinguishable, reverberation occurs.
What is Noise Pollution?
Noise pollution occurs in large cities because of traffic and the mechanization of human activities, and it is an important environmental problem.