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Physics (4.3 (Reflection (When light reflects off a very smooth surface…
Physics
4.3
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Reflection
When light reflects off a very smooth surface such as a mirror or a window, it undergoes regular reflection this produces a clear image
we see most objects, such as the Moon, because light bounces off them and then into our eyes this is called reflection
Properties of light wave
Like a sound wave electromagnetic wave has a specific frequency and wavelength, but unlike a sound wave, and electromagnetic wave does not require a material to transmit through, it
Light travels through space from the sun to the earth, lighting up our day, light is an example of electromagnetic radiation
Virtual image
Some light from the candle flame hits the mirror and is reflected towards your eyes. You see the light from the flame of the candle as though the light travelled in a straight line from a point inside the mirror. The candle shown on the right of the figure does not really exist. It is called a virtual image, a visual illusion created by your brain when you look into a mirror. The image you see in the mirror appears to be positioned as far inside the mirror as the object is positioned outside the mirror.
When a plane mirror produces an image of an object the image looks as though it is really positioned inside or behind the mirror.
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4.1
Heat vs Tempertaure
Temperature - the average speed (average kinetic energy) of the particles. It is how hot something is
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Units of Temperature
Fahrenheit: absolute zero - 459F, freezing point of water - 32F, boiling point of water - 212F
Kelvin: absolute zero - 0K, freezing point of water - 273K, boiling point of water 373K
Celsius: absolute zero - 273C, freezing point of water, 0C, boiling point of water 100C
The particle model
In liquids, particles are closely packed, the particles vibrate but are also free to move or flow over each other
In gases, particles are not bound together at all and are free to move in straight lines until they collide with other gas particles, or walls of the container held in.
In solids, the particles are closely packed, the particles vibrate on the spot keeping the shape of the object
Heat transfer
Convection - heat is transferred by convection in liquids and gases because their particles can move around, particles become less dense and more upwards, then cool and become dense and fall (convection current)
Radiation - radiation transmits heat as invisible waves that travel at the speed of light, which is around 300 000 km/s. Infrared radiation is heat energy that is transmitted this way. All objects emit (release) some infrared radiation.
Conduction - when heat is transferred by two touching objects e.g. particles near the flame vibrate more as they absorb heat energy, these vibrations transfer energy to conduct heat along the solid
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4.2
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SONAR
In this process, a ship sends a sound wave into the water. The sound wave bounces off any hard surfaces in the water such as fish. We can calculate the depth of objects under water by measuring the time a sound wave takes to bounce off them and return to the ship/surface
The time difference between sending and receiving sound waves can be measured. This difference can be used to calculate the depth of objects under water, using a technique called sonar (sound navigation and ranging)
Speed of Sound
The speed that sound travels through a material depends on the qualities of the material. In general, if a sound wave hits a dense material, made of lots of particles closely packed together, then the compressions and rarefactions will travel quickly. As a result, sound travels faster through solids than through liquids, and faster through liquids than through gases. The average speed of sound is 331m/s