"Energy moves in cycles, circles, spirals, vortexes, whirls, pulsations, waves and rhythms-rarely if ever in simple straight lines." -Starhawk
While studying the scientific discipline of physics, pupils will come to the realization that energy can be transferred and moved in many different ways.
In the sixth topic of the GCSE Physics Syllabus, students learn more about how waves are one of the ways in which energy can be transferred.
By examining the sections included in this topic of the syllabus such as the properties of waves, transverse and longitudinal waves, reflection and refraction, sound and ultrasound, lenses and black body radiation, students will acquire knowledge that will help them in their future scientific career.
Superprof will now consider the information explored by pupils in the GCSE Physics Syllabus from the AQA exam board in the United Kingdom.
Properties of Waves
Waves are one of the many ways energy can be transferred between stores. They can be described as oscillations or vibrations and it is important to note that all waves transfer energy but they do not and will not transfer matter.
Waves have many different parts and they can be described using the following terms:
- Rest position,
- Time period,
Diagrams are examined by pupils to further understand the location of the different parts of the waves.
Wave Period and Wave Speed
The time period a wave can be calculated using the following equation:
(Image is courtesy of bbc.com/bitesize/guides)
The period of time is measured in seconds and the frequency is measured in Hertz.
After the time period of a wave has been determined by pupils, they next move onto the equation of the wave speed which is the following:
wave speed = frequency x wavelength
After analyzing the aforementioned part of the properties of waves section, pupils measure the speed of sound in the air and in the water. Scientists have discovered that the air is made up of many tiny particles and when sound is created they vibrate and collide with each other causing the vibrations to pass between air particles. Using a simple equation, such as the following, the speed of sound can be gauged:
In the aforementioned equation, speed is measured in metres per second, distance is measured in metres and time is calculated in seconds.
Before this section is completed, pupils are expected to accomplish two required practicals. The first one has the aim of measuring the frequency, wavelength and speed of waves in a ripple tank and the second experiment has the goal of calculating the frequency, wavelength and speed of waves in a string.
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Transverse and Longitudinal Waves
There are two types of waves: transverse and longitudinal. The electromagnetic waves are transverse waves and have many different properties and various uses. Sound waves are longitudinal and the vibrations are parallel to the direction of wave travel.
Some examples of longitudinal waves include sound, ultrasound and seismic-P waves.
These waves show areas of compression, regions of high pressure due to the particles being close together, and rarefaction, low pressure because particles are spread farther apart.
A few examples of transverse waves include the ripples on the surface of the water, vibrations from a guitar string and the electromagnetic waves from a microwave.
Transverse waves are different from longitudinal waves due to the fact that the vibrations are at right angles to the direction of wave travel.
These are transverse waves and they transfer energy as radiation to an absorber and can travel through a vacuum at 300 million metres per second (m/s).
The electromagnetic spectrum shows in which ways waves have a variety of uses in different areas. Here are some of the most common uses per section of the spectrum:
- Radio waves: used for communication such as in television and radio,
- Microwaves: for household microwaves used for cooking and for satellite communications,
- Infrared: the infrared light can be seen in electric heaters and in infrared cameras that can detect people in the dark,
- X-Rays: used by health-care professionals to detect broken bones in a patient.
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Reflection and Refraction
All waves will either reflect or refract depending on the right circumstances. Humans can see images or colour based on the reflections and refraction of light.
The reflection waves of sound cause echoes and the reflection waves of light can be observed in different ways. Pay close attention to the following examples:
- Specular reflection: this reflection can be observed from a smooth and flat surface. This can be seen in a mirror and the image is upright and virtual,
- Diffuse reflection: if the surface is rough the reflected light will be scattered in all directions. This can often cause a distorted image that does not well reflect the original.
Students of any scientific discipline clearly recognize that materials will have varying densities. Refraction is the change in direction of a wave at the boundary between two clear materials. It can cause optical illusions and the density of a material affects the speed of the wave.
For example, the light passing through a dense transparent material will travel slower than it would if the material was less dense.
FAST which stands for Faster - Away/ Slower -Towards is an essential formula for remembering the speed and direction changes of light during refraction.
To put their newly acquired knowledge into practice, students are obliged to complete a required practical experiment that has the aim of investigating the reflection of light by different types of surface and the refraction of light by different substances.
Sound and Ultrasound - Higher
Sound has been scientifically proven to be caused by the vibration of particles. However, it is important to note that not all vibrations can be heard as sounds.
Sound waves are longitudinal waves and the vibrations can travel through solids, liquids or gases. Sound has different properties such as frequency and amplitude.
For example, high-frequency sound waves are high pitched and low-frequency sound waves are low pitched. When it comes to amplitude, high amplitude sound waves are loud and low amplitude sound waves are quiet.
Students also learn how to read oscilloscope traces to determine if the sound is quiet or loud and if the pitch is high or low.
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Ultrasound waves have a higher frequency that the human ear cannot hear. Ultrasounds have different uses such as the following:
- Breaking kidney stones,
- Cleaning jewelry.
The vibrations of the high-frequency ultrasound break up the kidney stones and the dirt that was damaging the jewellery. Nevertheless, when a person hears the word, 'ultrasound', babies come to their mind. This is due to the fact that ultrasound images create pictures of something that cannot be seen directly such as unborn babies or faulty organs in the human body.
Images are projected on machines as a result of the fact that the ultrasound waves meet the boundary between two different materials.
Echo sounding is accomplished by sending high-frequency sound waves into deep waters to detect objects and measure the depth of the water.
These waves are produced by earthquakes in the Earth's crust and there are two different types, P-waves and S-waves. They are very different from each other and have very identifiable properties such as:
- P-waves: these ones are longitudinal waves, are faster and can travel through solids and liquids,
- S-waves: are transversal waves, slower than the aforementioned and can only travel through solids.
The careful study of seismic waves done by scientists provides helpful evidence for the internal structure of the Earth.
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Lenses are precisely shaped pieces of glass that have been created for use in reading glasses, microscopes, telescopes etc.
There are real and virtual images that can be formed on a lens. A real image is an image that can be projected onto a screen and a virtual image often appears to come from behind the lens. Lenses can also be divided into two sections, convex and concave.
The images on convex lenses depend on the lens used and the distance from the object to the lens. Cameras and human eyes contain convex lenses and the image seen can be inverted, diminished or real.
Concave lenses always produce images that are upright, diminished or virtual. Peephole lenses are a good example of concave lenses. Students examining this section learn the primary differences between convex and concave lenses.
Lenses and curved images can produce magnified images. Magnification is the size of an image compared to the size of the object. Magnification can be calculated using a basic equation:
(Image is courtesy of bbc.com/bitesize/guides)
Since magnification is a ratio of two lengths, it has no units.
Absorption and Transmission of Light
When waves are absorbed by a surface, the energy of the wave is transmitted to the particles in the surface. At the moment when white light shines on an opaque object, colours of light are absorbed. The absorption of the other colours in the spectrum of white light is the reason why certain objects have defining colours that can be identified by the human eye.
Common materials such as air, glass and water are very good at transmitting light with very little absorption and that is why they appear transparent to the human eye.
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Black Body Radiation
Black bodies or objects are perfect absorbers and emitters of radiation. A perfect black body does not exist but if it did it would be able to absorb all the radiation that falls on it and it would not reflect or transmit any radiation.
It is important to note that an object that is a good absorber is also a good emitter.
The worse known absorbers and emitters are white and shiny objects since they reflect all visible light wavelengths.
The Earth's Temperature
There are many factors that contribute to the temperature of the Earth. These factors include the concentration of greenhouse gases such as water vapour, methane and carbon dioxide. Students learn all about these factors with more depth while studying this section of the GCSE Physics Syllabus.
Before finishing this section a required practical examination with the purpose of investigating how the amount of infrared radiation absorbed by a surface depends on the nature of that surface.
Sample Exam Questions
Knowing what type of answers to expect on an examination greatly increases the confidence of students. The GCSE Physics subject assessments are divided into two sections: the first four topics on the first exam and the last four topics on the second exam.
The question types are the same and examples that could be on the test are offered on the internet in order to be studied with anticipation. Here are the question types:
- Multiple choice questions,
- One and two mark questions,
- Three and four mark questions,
- Maths questions,
- Practical questions,
- Six mark questions,
For more information and examples of each type of question that might be considered on the exam, the BBC Bitesize website offers invaluable help.
Learning more about the topic of waves will further prepare students for a scientific career and set them on the right path towards completion of the GCSE Physics Syllabus.
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