Physics: WavesBy: Daisy Sowah, Neel Shah, Brian

Vlaar and Nii Adjei Ala-Lomo

What are waves?

• Wave motion is a form of disturbance which travels through a medium due to the repeated periodic motion of the particles of the medium about their mean positions, the motion being handed over from one particle to another.

Types of WavesThe waves which can be produced or propagated only in a material medium are called elastic or mechanical waves.

The waves which do not require a medium to propagate are called electromagnetic waves.

Types of wave motion

When the particles of the medium vibrate about their mean positions in a direction perpendicular to the direction of propagation of disturbance, the wave motion is called the transverse wave motion.

When the particles of the medium vibrate about their mean positions in the direction of propagation of disturbance, the wave motion is called the longitudinal wave motion

Some Wave Terms

Frequency – Number of complete waves passing a point each second. (Hz)

Displacement – Distance and direction from equilibrium position

Amplitude – Maximum displacement of vibrating particle from equilibrium position

Wavelength – The least distance between 2 adjacent vibrating particles ie. 2 peaks or troughs

Wave cycle - From one maximum displacement to the next maximum displacement

Wave Period – Time for one wave to pass a fixed point

Intensity is the measure of how much energy a wave is carrying. It can also be defined as the rate of flow of energy per unit area at right angles to the direction of travel of a wave (W/m)

Wave Phases• Phase Difference is the amount by

which two cyclical motions of the same frequency, are out of step with each other. It can be measured in degrees, radians, or seconds of time.

• leading phase refers to a wave that occurs "ahead" of another wave of the same frequency.

•  Lagging phase refers to a wave that occurs "behind" another wave of the same frequency.

• When two signals differ in phase by -90 or +90 degrees, they are said to be in phase quadrature .

• When two waves differ in phase by 180 degrees (-180 is technically the same as +180), the waves are said to be inphase opposition .

Coherent waves are waves with a constant phase difference. (Note: They don't have to be in phase for this to be true.) They will have the same frequency and wavelength (they are normally produced from one source).

Phase Difference

Diffraction• A wave will diffract (spread out)

as it goes through a gap or past an obstacle but the wavelength remains the same before and after the gap.

• The nearer the slit size is to the wavelength, the more the wave will diffract.

• The smaller the gap the greater the diffraction.

• The longer the wavelength the greater the diffraction.

Interference and Superposition

.If two waves of the same type and the same frequency combine so that the crest of one coincides with the trough of the other, they will completely cancel each other out.This is called destructive interference.Alternatively, the two waves could combine when their crests coincide; then there would be constructive interference and the resultant amplitude would be equal to the sum of the separate amplitudes:

When two waves meet they will interfere and superpose. After they have passed they return to their original forms. This is true if they are coherent or not.At the point they meet, the two waves will combine to give a resultant wave whose amplitude (or intensity) may be greater or less than the original two waves.The resultant displacement can be found by adding the two displacements together

Principle of Superposition: When two or more waves of the same type meet at a point, the resultant displacement of the waves is equal to the vector sum of their individual displacements at that point.

Interference may be described as the superposition of waves from 2 coherent sources

Thank you for you time