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Science |
Middle Years Science Program - Light & Sound Science Show |
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Middle Years Science Program
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Return to Science Shows  Program: St Anne's (Maureen & Kym) Presentation: Equipment:
Notes: Sound Sound requires a medium (or material) to travel through. If there was no air then there would be no sound. This means movies like Star Wars would not be able to hear explosions in space. In fact, explosions would not occur since there is no air to combust the fuel. If the air in your classroom is removed then there would be no way to transmit sound. The sense of hearing is made by your ears ...
Sound from some sound source travels through the air by longitudinal waves: air particles bounce into one another in a series of collisions towards your ear. It strikes your ear drum: a very fine skin membrane. It vibrates and strikes the anvil and stapes which act like a hammer touching the surface of the ear drum. The sound is transferred to the fluid in the inner ear. Within the cochlea are very fine hairs that ranging in size from large to fine. The different lengths of hair are used to record different frequencies of sound as the sound wave spirals around towards the centre of the cochlea. In later life we start to lose our hearing which in effect is the death of these finer hairs. The semicircular canals in which the sound also passes allows us to detect balance. If you get your ears flushed it is the mixing up of the fluid within these canals that make us dizzy. The Eustachian tube maintains appropriate air pressure within your ear and connects your ear to the roof of your mouth. The outer ear is used to amplify and direct the sound wave concentrated into your ear canal and then the ear drum. The auditory nerve takes the signals from the cochlea to your brain. If you go to a loud concert upon leaving your ears often are "ringing". Your ear is a very clever organ. It registers that there is too much sound and as a result will pull the anvil and stapes back away from close contact with the ear drum that is very delicate allowing it more room to move. This effect is the ringing in your ears. It gradually moves back into position when it realises the sound levels are safer. An echo is caused when sound reflects from its source by large surfaces This is the basis for Sonar in ships. The time it takes to return can then work out what objects and the location of objects under water for submarines and ships. Music The timbre of a certain sound distinguishes the note of the same pitch on different instruments This depends upon the shape of the sound wave. Loudness is related to the amount of sound energy the sound wave carries and depends upon the size and pitch. Pitch is related to the frequency of a sound wave. High-pitched instruments have high frequencies and visa versa. Generally, if you double the frequency you will get the same note an octave higher. In the sound production industry microphones and loudspeakers have been designed with the sole purpose of receiving and transmitting sound. In both cases, a diaphragm vibrates and an electrical signal is transmitted or created as a result. The cone of a loudspeaker vibrates as a result of an electrical signal received from a microphone. The stronger the signal from the microphone, the stronger the vibration in the cone of the loudspeaker. Musical Instruments
In all cases, longitudinal
waves will result: air particles move along length of wave. Speaking and Hearing Lungs act as a source of air allowing the vocal chords to vibrate like a vibrating set of strings. The air flows into the lower throat, mouth and nasal cavity. Our vocal tract acts like a closed pipe and the length of the "pipe" is controlled by the larynx. Much the same as a trombone changes in length by changing the length of the pipe ...
Light Structure and function of the eye The eye is made up of various parts which aid in the process of forming images. The rear screen that the light is focussed on is called the retina. It has millions of cells sensitive to light which send the signal to the brain via the optic nerve. On the retina, there are two types of cells: rods and cones (responsible for black and white, and colour perception). The transparent part of the eye in the front that light first passes through is called the cornea. It curves around the actual lens behind which bends the light depending on how curved it is. Special muscles on the top and bottom of the lens can stretch the lens to be more narrow or wider. This allows the image to focus closer or further away from the lens. When we see a blurred object, the image is not focussing on our retina. Light will travel through a hole in the iris (the coloured section of the eye) called the pupil (which is black because it is simply a hole that light disappears through). In a dark room this iris aperture opens up. Light Rays The sun is the source of most of the light we see. The sun is luminous because it emits its own light (like a candle or torch). Non-luminous objects reflect the light bouncing off it (e.g. the moon). We are non-luminous. Usually light travels in straight lines. Paths of light are represented by straight lines in ray diagrams. Light spreads out from a point source in all directions. Objects can also be classified as incandescent: they emit light because they are hot (flames and light bulbs). Some animals are classified as bioluminescent: they emit light without heat (e.g. fireflies, glow worms, or some deep sea angler fish). How does Light Travel Shadows are
formed because light travels in straight lines otherwise the shadow
will not be the same shape as the object. Shadows can be fuzzy or sharp
depending on the size of the source of light. The darkest part of the
shadow is called the umbra and the lighter part on the outside
is called the penumbra. As the light source gets smaller or further
away, the penumbra gets smaller and the shadow gets sharper.
Energy Conversion for Light & Sound Match them up activity: Flash cards with the correct type of conversion of energy ...
Demonstrations:
Theory of Energy:
The most important thing is that energy is something that we all need and can use. It is important that we use it and to know where it came from in the first place. The reason we can get up every morning and go to school to learn and have fun is because we keep refuelling ourselves with food. Like putting petrol into cars to make them work. Without the petrol cars will not run. We have to do the same. How many times have your heard your Mum or Dad say "You must eat all your dinner first". We will look at different types of light and sound energy and how they might change from one form to another. Changing and storing energy: Almost all energy we use today comes indirectly from the Sun. Most of the energy reached the Earth millions of years ago and is now stored in the form of coal, oil or natural gas. This form of stored energy must be converted into other forms of energy to be useful for factories, homes, communication and transport. When energy changes from one form to another some of the energy is lost. Other examples of sound and light energy converters could include the following ...
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