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Candidates should use their skills, knowledge and understanding of how science works:
- Sound waves can travel through solids causing vibrations in the solid.
- Within the ear, sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound. The conversion of sound waves to vibrations of solids works over a limited frequency range. This restricts the limits of human hearing.
- Students should be able to:
- describe, with examples, processes which convert wave disturbances between sound waves and vibrations in solids. (Examples may include the effect of sound waves on the ear drum)
- explain why such processes only work over a limited frequency range and the relevance of this to human hearing.
- Students should know that the range of normal human hearing is from 20 Hz to 20 kHz.
- Ultrasound waves have a frequency higher than the upper limit of hearing for humans. Ultrasound waves are partially reflected when they meet a boundary between two different media.
- The time taken for the reflections to reach a detector can be used to determine how far away such a boundary is. This allows ultrasound waves to be used for both medical and industrial imaging.
- Echo sounding, using high frequency sound waves is used to detect objects in deep water and measure water depth.
- Seismic waves are produced by earthquakes. P-waves are longitudinal, seismic waves. P-waves travel at different speeds through solids and liquids. S-waves are transverse, seismic waves.
- S-waves cannot travel through a liquid. P-waves and S-waves provide evidence for the structure and size of the Earth’s core.
- Students should be aware that the study of seismic waves provided new evidence that led to discoveries about parts of the Earth which are not directly observable.
- Students should be able to explain in qualitative terms, how the differences in velocity, absorption and reflection between different types of wave in solids and liquids can be used both for detection and exploration of structures which are hidden from direct observation.
- A lens forms an image by refracting light.
- In a convex lens, parallel rays of light are brought to a focus at the principal focus.
- The distance from the lens to the principal focus is called the focal length.
- Ray diagrams are used to show the formation of images by convex and concave lenses.
- The image produced by a convex lens can be either real or virtual.
- The image produced by a concave lens is always virtual.
- Students should be able to construct ray diagrams to illustrate the similarities and differences between convex and concave lenses.
- The magnification produced by a lens can be calculated using the equation:
- magnification = image height /object height
- Magnification is a ratio and so has no units.
- Image height and object height should both be measured in either mm or cm.
- In ray diagrams a convex lens will be represented by:
- A concave lens will be represented by:
- LOGON SCIENCE CODES:
126.96.36.199, 188.8.131.52, 184.108.40.206, 220.127.116.11, 18.104.22.168, 22.214.171.124, 126.96.36.199
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