Grade 11 ↓
Waves and oscillations
The study of waves and oscillations is an integral part of physics. These concepts are fundamental in describing a variety of phenomena in science and engineering. From light ripples on a pond to the sound of musical instruments and even the electromagnetic waves that enable wireless communication, waves and oscillations are all around us. Understanding them can provide insights into how the universe behaves at both the macroscopic and microscopic levels.
Introduction to waves
A wave is a disturbance that travels from one place to another through a medium or vacuum. The medium can be a solid, liquid, gas, or even the vacuum of space. Waves transfer energy from one point to another without the physical transfer of particles from one place to another.
Types of waves
Waves can be classified based on the direction of particle displacement with respect to wave propagation:
1. Mechanical waves
These require a medium to travel. Examples include sound waves, seismic waves, and water waves.
Longitudinal waves
In longitudinal waves the particles of the medium vibrate parallel to the direction of wave propagation. Sound waves in air are a classic example of this.
Example: Sound waves in air, compressions and rarefactions.
Transverse waves
In transverse waves the particles of the medium move perpendicular to the direction of wave propagation. Light waves and waves on a string are typical examples of this.
Example: Waves on a string, water surface waves.
2. Electromagnetic waves
Electromagnetic waves do not require a medium to propagate. They can also travel through a vacuum. Examples include light, radio waves, and X-rays.
Wave characteristics
Understanding waves requires knowledge of several key characteristics:
Wavelength ( λ )
Wavelength is the distance between successive crests or troughs in a wave. It determines the length of the wave and is measured in meters.
Frequency ( f )
Frequency refers to how many times the particles of a medium vibrate when a wave passes through it. It is measured in Hertz (Hz), which is equal to cycles per second.
Dimensions
The amplitude of a wave is the maximum displacement of the particles of the medium from their equilibrium position. It represents the energy and intensity of the wave.
Wave speed
The speed of a wave is the distance travelled per unit time by a point (such as a crest) on the wave. The speed ( v ) of a wave can be calculated using the formula:
v = f * λ
where v
is the speed of the wave, f
is the frequency, and λ
is the wavelength.
Introduction to oscillation
Oscillations are back-and-forth movements at a regular interval. A classic example of an oscillating system is a simple pendulum. When it is displaced from its equilibrium position, it experiences a force that tends to move it back towards equilibrium, creating an oscillatory motion.
Simple harmonic motion (SHM)
Simple harmonic motion is a type of oscillation in which the restoring force is proportional to the displacement and acts opposite to the direction of displacement. SHM is characterized by oscillations having a sinusoidal waveform.
Features of SHM
- Equilibrium position: The position where the net force on the system is zero.
- Amplitude ( A ): Maximum displacement from the equilibrium position.
- Period ( T ): The time taken in one complete cycle of oscillation.
- Frequency ( f ): The number of oscillations per unit time. It is the inverse of the period.
f = 1 / T
Mathematical representation of SHM
Motion can be described using a sine or cosine function. If x(t)
represents displacement as a function of time, then:
x(t) = A * cos(ωt + φ)
where A
is the amplitude, ω
is the angular frequency, t
is time, and φ
is the phase angle.
The angular frequency is related to the frequency and period as follows:
ω = 2πf = 2π/T
Energy in SHM
In SHM the energy is continuously transformed between potential energy and kinetic energy while the total mechanical energy remains constant.
Practical examples and applications
Pendulum
The pendulum is one of the most common examples of oscillations. The time period of the pendulum depends on its length and the acceleration due to gravity as shown below:
T = 2π √(L/g)
Where L
is the length and g
is the acceleration due to gravity.
Mass-spring system
Another classic example of SHM is a mass attached to a spring. According to Hooke's law, the force exerted by the spring is proportional to the displacement:
F = -kx
Where k
is the spring constant, and x
is the displacement.
The time period of oscillation for a mass m
on a spring is given by:
T = 2π √(m/k)
Waves in everyday life
From the music we listen to, the light we see every day, and the radio waves that carry data to our phones, understanding waves helps us understand how our technology and environment work.
Conclusion
Waves and vibrations are everywhere around us and form the backbone of many scientific theories and techniques. From understanding the nature of sound and light to the behaviour of quantum particles, the principles of waves and vibrations form the basis of many advances in science and technology.