O Level Physics Chapter :11: Properties of Waves

Prepared By: Shakil Raiman

11.1: Waves Waves are a means of transferring energy and

information from one place to another. These transfer takes place with no matter being

transferred. For example, energy can be carried by a water wave

generated by a boat out at sea to the shore, or by a sound wave from the loudspeaker to an audience’s ears.

The most common waves found in daily life are water waves, sound and electromagnetic waves.

11.2: Types of Waves

Two types of waves: Transverse wave Longitudinal Wave

11.3: Transverse Wave

A transverse wave is a wave in which the vibrations of the particles are at right angles to the direction of propagation of the wave.

EXAMPLES OF TRANSVERSE WAVES: Microwaves, radio waves, infra-red, visible light,

ultra-violet, X-rays and -rays are called electromagnetic waves. All these waves are transverse waves. Another example is water wave.

11.3.1: Transverse Wave

11.4: Longitudinal Wave

A longitudinal wave is a wave in which the vibrations of the particles are parallel to the direction of propagation of the wave.

EXAMPLES OF LONGITUDINAL WAVES: Sound wave

11.4.1: Longitudinal Wave

11.5: Describing Waves

11.5: Describing Waves: Amplitude and Wavelength: Amplitude: The amplitude of a wave is the maximum

displacement of a particle from its resting position. SI unit is metre (m).

Wavelength: The wavelength of a wave is the minimum distance at which the wave repeats itself. It can also be taken as the distance between two successive crests ( or troughs). It is denoted by (lambda). SI unit is metre (m). In case of longitudinal wave, wavelength is the distance between

two successive centres of compression (or rarefaction)

11.5: Describing Waves: Time Period and Frequency: Period or Time Period: The period of a wave is the

time taken for one complete vibration of a particle. It is also the time taken to produce one complete wave. It is denoted by T. SI unit is second (s).

Frequency: The frequency of a wave is the number of complete waves produced per second. It is denoted by f. SI unit is hertz (Hz).

The relationship between period and frequency is:

Tf

1

11.6: Wave Speed

The speed, v, of a wave is the distance traveled by the wave in one second.

The wave moves by a distance of one wavelength () is one period (T), so the wave speed (v) is:

As, so, v = f

Ttime

cedisv

tan

Tf

1

11.7: Worked Examples

11.8: Ripple Tank A ripple tank is a

shallow glass tank of water used in schools and colleges to demonstrate the basic properties of waves.

When the motor is turned on the wooden bar vibrates and produce waves.

11.8.1: Ripple Tank A ripple tank

can be used to produce waves to investigate the wavelength, amplitude and frequency of a wave.

11.9: Reflection of Wave Reflection is the change in direction of a wavefront

at an interface between two different media. Laws of reflection:

The incident ray, normal and the reflected ray all lie on same plane.

The incident angle (i) = the reflected angle (r)

Normal is a line drawn at right angles to the surface (at the point of incident ray).

11.9.1: Reflection of Wave

11.9.2: Reflection of Wave

11.10: Refraction of Wave

Refraction is the change in direction of a wave due to a change in its transmission medium.

Laws of refraction: The incident ray, normal and the refracted ray all lie on

same plane.

indexrefractiveconst

r

i_.

sin

sin

11.10.1: Refraction of Wave

11.11: Diffraction of wave

Diffraction is the spreading of waves while passing through narrow gap.

If the gap is close to the wavelength of the wave diffraction is most.

Examples of diffraction include sound waves that diffract as they pass through doorways.

Diffraction also happens when waves pass a single edge. Radio waves are diffracted as they pass over hills.

11.11.1: Diffraction of wave

11.11.2: Diffraction of wave

Thank You All

Wish you all very good luck and excellent result.