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Chapter 2: Energy Transfer Through Waves - Coggle Diagram
Chapter 2: Energy Transfer Through Waves
2.1 How can wave be produced using a rope or a spring to transfer energy?
A wave is made up of motion that repeats itself after a period of time
A wave motion can be produced using a rope with a fixed end
When a person holds one end of the rope and moves his hand up and down continuously, a series of waves are formed. The waves move from left to right.
The kinetic energy from the movement of the hand is transferred through the rope to the fixed end. The rope is the medium through which the wave travels.
If the ribbon is tied to one point of the rope, the ribbon will be seen moving up and down but not to the right. This shows that the rope wave transfers energy but does not transfer any part of the rope itself.
Therefore, a wave transfers energy through vibrations without transferring any part of the medium.
Types of wave motion
A wave motion can be produced using a slinky spring by moving one end up and down while keeping the other end fixed.
The direction of vibration (up and down) is perpendicular to the direction of the wave (left and right).
Another type of wave motion can be produced with a slinky spring by moving one end of the spring back and forth while keeping the other end fixed. In this setup, energy is also transferred from the vibrating end to the fixed end.
A series of dark and light bands are formed. The dark band are parts of the coil which are being compressed and the light bands are parts of the coil which are extended.
The direction of vibration is parallel to the direction of the wave.
2.2 How can a wave be described?
Crests are the highest point of wave
Troughs are the lowest points of wave
Amplitude is the maximum displacement from the rest position. It is the height of a crest or depth of a trough measured from the rest position. Its SI unit is the metre (m)
The amplitude of a wave is related to the energy which it transfers. The greater the energy a wave transfers, the larger its amplitude.
Similarly, the wave of a loud sound has larger amplitude than the wave of a soft sound.
Wavelength is the distance between two successive crests or two successive troughs.
Frequency (f) is the number of complete waves produced per second. The SI unit is the hertz (Hz). For example, when two complete waves are produced in one second, the frequency is 2Hz. Other larger units are kilohertz (kHz) and megahertz (mHz)
2.3 What are the different types of electromagnetic waves and their uses?
The light that helps us to see is a type of electromagnetic (EM) wave.
Besides light, there are other types of electromagnetic waves:
gamma rays
X-rays
ultraviolet
infrared
microwaves
radio waves.
Together, these waves form the electromagnetic spectrum.
In the EM spectrum, the EM waves are arranged in the order of frequency or wavelength.
Radio waves have the longest wavelengths and the lowest frequencies
Gamma rays have the shortest wave lengths and the highest frequencies.
These electromagnetic waves have many important uses in our daily lives.
Radio Waves
Radio waves are the EM waves that transfer music from the radio station to your radio set. Besides radio broadcasting, radio waves are also used for TV broadcasting, radar and global positioning systems (GPS)
Radio waves have also brought us many conveniences by making it possible to go wireless. The EZ-link fare card for taking public transport and the Electronic Road Pricing (ERP) gantries both use radio wave technology.
Microwaves
The most well-known use of microwaves is probably a microwave oven. In the microwave oven, the microwaves cause the water particles in food to vibrate, creating friction which heats up the food in short time.
Besides cooking, microwaves are also used in mobile phone and satellite communication.
Infrared Waves
Most television sets come with a remote control unit that allows us to change channels or adjust the volume without leaving our seats. Remote control units use infrared waves to transmit information to television set.
Infrared waves are also known as heat waves. The hotter an object, the more infrared the object gives out. The infrared thermometer measures the amount of infrared waves given out by out body to determine our body temperature.
Visible light
Visible light is the only type of EM wave that we can see. The colours that we see are actually light waves of different wavelengths
Besides helping us to see, light is also used by plants to perform photosynthesis.
Light is also used for high speed data transmission through optical fibres.
Ultraviolet waves
A forgery detector emits ultraviolet waves which cause special features on a real bank note to glow.
Ultraviolet wave in the sunlight cause our bodies to become tanned. Ultraviolet also helps our bodies to produce vitamin D which helps to strengthen our bones and protect children against rickets (bone disease). However, it is important not to be overexposed to ultraviolet which can cause sunburn and is linked to skin cancer.
Another application of ultraviolet is to kill microbes and sterilise medical equipment.
X-rays
X-rays are used to produce images of the body´s internal organs and bones. This helps doctors check for bones fractures and other health conditions.
X-rays are also used in airports to scan luggages for prohibited items.
Gamma rays
It is used for radiation therapy. These are high energy rays are directed at cancer cells to kill them. Gamma rays can also be used to sterilise medical equipment.