The maximum distance a particle moves in a wave is the Transverse wave.
The movement of a particle back to its starting point is called the oscillation.
The distance between two peaks on a wave is the wavelength.
The number of waves per second is frequency.
The distance between the peak of one wave and the next is the wavelength.
Ultrasound is high frequency sound which we cannot hear. It can go through the softer tissues of the human body. It is reflected whenever it travels from one type of material to another.
Scanning is building up a picture in sections or pieces. During an ultrasound scan of an unborn baby the head shows up clearly because it has a greater density than the surrounding tissue. This causes better reflection. An advantage of ultrasound scans iss that the wave's energy is reflected rather than absorbed by the foetus, so it does not harm the baby. A disadvantage is that the wave is scattered in all direction when it is reflected.
Wave Speed Equation:
speed= distance covered by the wave / time taken
Any wave that is not reflected will continue to travel through the new material. The new material will usually cause the speed of the wave to change. This is called refraction and the wave usually changes direction.
Earthquake waves are usually known as seismic waves, can cause a frightening amount of damage. They can also tell you about what lies beneath the Earth's surface.
The wave Equation
The speed of a wave can be calculated by the wave equation:
speed= frequency x wavelength
Lowest frequency and long wavelength
High frequency and short wavelength
The wave equation continued
The electromagnetic spectrum of waves includes radiowaves, microwaves, infrared, visible light, ultraviolet, xrays and gamma rays.
All electromagnetic waves travel with the same speed in a vacuum. This speed is called the speed of light. They are all transverse waves.
Using electromagnetic waves
Radiowaves can get through brick walls, so you can lsiten to the radio at home. When a wave passes through something it penetrates it. There are limits to what materials radiowaves can penetrate. Car radios fade in tunnels. Different parts of the electormagnetic spectrum can penetrate different materials.
If you travel through an airport you need your passport for identification. Many airports now scan your iris. This is called iris recognition.
Objects emit radiation due to their temperature. You may see the emission of visible light if objects are very hot. Hot objects actually emit a range of different types of electromagnetic radiation. a light bulb emits visiblep light because the filament is very hot.
More uses of electromagnetic waves
Broken bones can be detected using xray absorbtion. Absorbtion means that some of the wave energy is transferred to the material. If there is a break or fracture in the bone then xrays penetrate through the break.
Meteorologists need information about the current climate to predict the weather. In heavy rain your mobile phone will have poor reception. Mobile phones use microwave radiation. Microwaves are absorbed by water.
Fluorescent inks are used to add invisible symbols to banknotes. These symbols show up under ultraviolet light.
Microwaves and mobile phones
Many households have a microwave oven. They use microwaves to heat food very quickly. Microwave radiation is absorbed by water and fat. Food with a high water content is particularly suitable for microwave cooking. At first people thought that they might absorb escaping microwaves, but microwave iovens have a metal grill in the front glass door to prevent microwaves escaping.
Mobile phones also make use of microwaves to communicate. When you make a call, microwaves are sent out from your phone. You head will receive a dose of microwave energy when you hold your phone next to your ear. Some of the radiation will be absorbed and it will heat some of the tissue in your head.
Harmful electromagnetic waves
X-rays are used for medical purposes, such as imaging bones, but even short exposure to xrays cause some tissue damage. Xrays can knock out electrons from atoms. If the atoms are in a human cell then xrays can destory cells. Xrays also damage Dna in the cell. Damge to DNA causes mutation which can lead to malfunction of cells and possibly cancer.
Ultraviolet radiation can ionise atoms. It can knock electrons out of atoms in a similar way to xrays and gamma rays. In cells this can lead to destruction or mutation and ultimately cancer.
Vinyl records store music in analogue form. Analogue means that a continously varying signal i produced when the record is playing. This is amplified and sent to a loudspeaker. The advantage of analogue is that it uses relatively cheap and simple equippment.
Morse code is a digital system of coding information. it uses two codes dot or dash. Modern digital communication systems use two states 0 or 1 or bits. The digital signals are processed directly by computers. The signal quality is better than anologue. Interference can still affect a digital signal but the decoding systen only has to interpret 0s and 1s. Digital information can be sent using electric wires but it can also be sent using anything that can be switched on and off, or turned low and high.
A weighty problem
Gravity is the force of attraction from the Earth that holds you on the ground. This force is called your weight. Your weight is six times greater on Earth thasn it would be on the Moon. Gravity affects our lives on Earth. Gravity forces the water out of a tap and it makes raindrops fall to the ground. To walk and run we have to overcome the force of gravity. Gravity traps our atmosphere and holds it close to Earth.
If a feather and a hammer are dropped at hte same time from the same height, they will hit the surface of the moon at the same time. each object falls with the same acceleration becasue of gravity. This acelleration is called aceleration due to free fall.
Our place in the Universe
The planets move in orbits around the Sun. lanets do not produce their own light. They reflect light from the Sun. There are also asteroids and comets. This is known as the solar system. Our Sun belongs to a huge group of stars known as the Milky Way galaxy. Our galaxy is spiral shaped, but we see it edge on. The galxy is spinning AROUND A CENTRE. The Milky way is one of millions of galaxies which make up the universe. Galaxies can be different shapes conmpared to the MIlky way.