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Properties of Waves

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Types of waves - Properties of waves - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

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Learn about and revise wave properties, calculations involving waves and measuring the speed of sound with GCSE Bitesize Physics.

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Transverse & Longitudinal Waves
[Including Electromagnetic Waves]

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In , the vibrations are parallel to the direction of wave travel.

Examples of longitudinal waves include:

One way to remember the movement of particles in longitudinal waves is to use the 'P' sound: longitudinal waves such as seismic -waves may be thought of as ressure or ush waves as the particles move arallel to the wave.

Demonstrating longitudinal waves

compressions are regions of high pressure due to particles being close together

rarefactions are regions of low pressure due to particles being spread further apart

Longitudinal waves are often demonstrated by pushing and pulling a stretched slinky spring.

In the diagram, the compressions move from left to right and energy is transferred from left to right. However, none of the particles are transported along a longitudinal wave. Instead, they move backwards and forwards between compressions as the wave is transmitted through the .

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Longitudinal waves - Transverse and longitudinal waves - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

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In , the vibrations are parallel to the direction of wave travel. Examples of longitudinal waves include: One way to remember the movement of particles in longitudinal waves is to use the 'P' sound: longitudinal waves such as seismic -waves may be thought of as ressure or ush waves as the particles move arallel to the wave.

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Reflection & Refraction

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- including sound and light - can be reflected at the boundary between two different materials. The reflection of sound causes echoes.

The law of reflection states that:

angle of incidence = angle of reflection

For example, if a light ray hits a surface at 32°, it will be reflected at 32°.

The and are measured between the light ray and the - an imaginary line at 90° to the surface. The diagrams show a water wave being reflected at a barrier, and a light ray being reflected at a mirror.

Specular reflection

Reflection from a smooth, flat surface is called . This is the type of reflection that happens with a flat mirror. The image in a mirror is:

In a , the rays appear to diverge from behind the mirror, so the image appears to come from behind the mirror.

Diffuse reflection

If a surface is rough, happens. Instead of forming an image, the reflected light is scattered in all directions. This may cause a distorted image of the object, as occurs with rippling water, or no image at all. Each individual reflection still obeys the law of reflection, but the different parts of the rough surface are at different angles.

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Reflection of waves - Reflection and refraction - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

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including sound and light - can be reflected at the boundary between two different materials. The reflection of sound causes echoes. The law of reflection states that: angle of incidence = angle of reflection For example, if a light ray hits a surface at 32°, it will be reflected at 32°.

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Properties of Waves

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Types of waves - Properties of waves - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

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Learn about and revise wave properties, calculations involving waves and measuring the speed of sound with GCSE Bitesize Combined Science.

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Transverse & Longitudinal Waves

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Longitudinal waves - Transverse and longitudinal waves - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

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In , the vibrations are parallel to the direction of wave travel. Examples of longitudinal waves include: One way to remember the movement of particles in longitudinal waves is to use the 'P' sound: longitudinal waves such as seismic -waves may be thought of as ressure or ush waves as the particles move arallel to the wave.

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Black Body Radiation

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There are no known objects that are perfect at absorbing or emitting all the radiation, of every possible frequency, that may be directed at it. Some objects do, however, come close to this and these are referred to as "black bodies".

A perfect black body is a object. It would have these properties:

An object that is good at absorbing radiation is also a good , so a perfect black body would be the best possible emitter of radiation.

Stars are considered to be black bodies because they are very good emitters of most wavelengths in the electromagnetic spectrum . This suggests that stars also absorb most wavelengths. Whilst there are a few wavelengths that stars do not absorb or emit, this figure is very low, so they can be treated as black bodies. Planets and black holes are also treated as nearly perfect black bodies.

Poor absorbers and emitters

White and shiny silvery surfaces are the worst absorbers, as they reflect all visible light wavelengths. Poor absorbers are also poor emitters, and do not emit radiation as quickly as darker colours. Radiators in homes are usually painted white so that the infrared radiation is emitted gradually.

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Emission and absorption of infrared radiation - Black body radiation - AQA - GCSE Physics (Single Science) Revision - AQA - BBC Bitesize

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There are no known objects that are perfect at absorbing or emitting all the radiation, of every possible frequency, that may be directed at it. Some objects do, however, come close to this and these are referred to as "black bodies". A perfect black body is a object.

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Reflection & Refraction

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- including sound and light - can be reflected at the boundary between two different materials. The reflection of sound causes echoes.

The law of reflection states that:

angle of incidence = angle of reflection

For example, if a light ray hits a surface at 32°, it will be reflected at 32°.

The and are measured between the light ray and the - an imaginary line at 90° to the surface. The diagrams show a water wave being reflected at a barrier, and a light ray being reflected at a mirror.

Specular reflection

Reflection from a smooth, flat surface is called . This is the type of reflection that happens with a flat mirror. The image in a mirror is:

In a , the rays appear to diverge from behind the mirror, so the image appears to come from behind the mirror.

Diffuse reflection

If a surface is rough, happens. Instead of forming an image, the reflected light is scattered in all directions. This may cause a distorted image of the object, as occurs with rippling water, or no image at all. Each individual reflection still obeys the law of reflection, but the different parts of the rough surface are at different angles.

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Reflection of waves - Reflection and refraction - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

# data[].attributes.attachment_link.description
including sound and light - can be reflected at the boundary between two different materials. The reflection of sound causes echoes. The law of reflection states that: angle of incidence = angle of reflection For example, if a light ray hits a surface at 32°, it will be reflected at 32°.

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Infared radiation absorption and radiation by a surface

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Investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface

There are different ways to investigate the amount of infrared radiation absorbed or radiated by a surface. It is important to:

use appropriate apparatus to measure and record temperature accurately

make observations regarding the effects of electromagnetic waves on different substances

The method described here uses a Leslie cube. This is a metal cube with four different types of surface. It is filled with hot water to increase its temperature.

Aim of the experiment

To investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface.

1. Place a Leslie cube on a heat-resistant mat. Fill it, almost to the top, with boiling water and replace the lid.

2. Leave for one minute. This is to enable the surfaces to heat up to the temperature of the water.

3. Use the infrared detector to measure the intensity of infrared radiation emitted from each surface, or the temperature of the surface. Make sure that the detector is the same distance from each surface for each reading.

Record results in a suitable table. The table below shows some example results:

Plot a bar chart to show the results. Make sure each bar is the same width and labelled clearly to show which surface it represents.

Use your results to order the different surfaces from the best emitter to the worst emitter of infrared radiation.

Evaluation

Explain why the detector must be placed the same distance from each surface before taking a reading.

Hazards and control measures

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Required practical - Infared radiation absorption and radiation by a surface - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

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There are different ways to investigate the amount of infrared radiation absorbed or radiated by a surface. It is important to: use appropriate apparatus to measure and record temperature accurately make observations regarding the effects of electromagnetic waves on different substances The method described here uses a Leslie cube.

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Sample Exam Questions

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Waves - Multiple choice questions - Sample exam questions - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

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Learn about and revise Waves exam questions with GCSE Bitesize Combined Science.