A wave is a disturbance that travels across the environment through a series of oscillations or vibrations. A wave transfers energy from one point to another. The  particles involved in it do not move from their position but do vibrate or oscillate. This oscillation forms the crests and troughs of the waves.

#### Types of waves

• Transverse waves are waves which oscillates perpendicular to the direction of the wave. The best example of this kind of wave is found in a pond when you throw a pebble in it. You can see a wave being produced by this action. This is a ripple wave. What this represents is that the particles of the water are not moving from their positions but vibrating, transferring their kinetic energy to the other particle. If you tie a rope to a wall and grab the other end and move it up and down continuously, you would see a wave produce on the rope while the rope itself does not move towards the wall even though the kinetic energy is being supplied to the wall.
• Longitudinal waves are those waves which have oscillations parallel to the direction of the wave. The best example of this kind of wave is if you attach a spring with a wall and then grab the other end and move the spring forward and backward continuously. You will notice a series of compression and rarefaction formed in the spring which are properties of the longitudinal wave.
• Electromagnetic waves are waves like light waves and radio waves etc. These waves can move through vacuum (empty space) as these oscillations are present in the electric and magnetic fields. All electromagnetic waves are transverse waves because they vibrate perpendicularly to the direction of the wave.
• Mechanical waves like the sound wave and ripple wave move through matter (medium). Mechanical waves can be transverse waves or longitudinal waves.

#### Defining Waves

Waves have few properties properties yet to be discussed.

• Amplitude is the height of a crest or the depth of a trough from the point of rest in a wave.
• Wavelength (λ) is the distance from one crest to the adjacent crest or the distance from one trough to the adjacent trough of the wave in a transverse wave. In a longitudinal wave the wavelength is calculated by measuring the distance from the middle of a compression to the adjacent middle of the compression or from the middle of the rarefaction to adjacent middle of the rarefaction.
• Frequency (ƒ) is the number of crests in a wave in 1 second or the number of troughs formed in 1 second.

To find the speed of a wave we can use the equation: v=ƒλ. v is for speed.

#### Wavefront

Wavefront is an imaginary straight line which joins all points which have the same vibration.

#### Reflection of waves

Waves tend to reflect when they touch a flat surface. The best example can be seen in ripple waves. If these waves touch a straight wall which is at an angle from the waves, the waves would then reflect to another direction. An imaginary straight line is made at an from the point at which the waves touch the wall, this is called the normal, the angle formed from the normal and the direction of the waves is called an angle of incidence. The angle formed from the normal and the point of reflection is called the angle of reflection.

#### Refraction of waves

Waves also refract just as well as reflect. The best example of refraction can be taken from the ripple waves. If a wave moves from deeper water to shallower water then the wave slows down and then refracts. This is because when the front part of the wave touches the shallower water it slows down, and then the rest of the wave follows up and slows down as well and this continues on while the wave refracts.

#### Reflection of Sound Wave

Like all waves sound also reflects. To prove this you should set up an apparatus as suggested. Place a hard flat surface. Place a clock with a wide tube reaching towards the flat surface. Then place another tube at the adjacent side of the other tube and listen through the tube. You should hear the clock ticking.

#### Refraction of Sound Waves

Sound waves tend to slow down in cold air and speed up in hot air meaning refraction happens in between the layers in the atmosphere. During day time the ground air becomes warmer while the air high up is colder which is why sound waves refract up wards. At night the air in ground is cold while the air high up is warmer causing the sound waves to refract downwards.