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58 Cards in this Set
- Front
- Back
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Why do planets stay in orbit around the sun? |
Gravity |
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What force is in the centre of any circular orbit? |
A centripetal force |
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What follows an inverse square law? |
Gravitational force |
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Why is the orbit time less for planets closer to the sun? |
-Travels a shorter distance -Greater gravitational force |
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A satellite moves at a _______ to gravity |
Tangent |
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What are the features of a polar orbit? |
-Orbit above North and South Poles -20 to 100km above earth -90mins to orbit earth -Used for imaging such as short range weather forecasting |
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What are the features of a geostationary orbit? |
-Orbits above the equator -24hr orbit -Used for communications -All must be in same orbit but not too close to eachother so as to not interfere signals via diffraction -36thousand km above earth |
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What quantity has only magnitude, versus one with magnitude AND direction? |
Scalar versus vector |
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How are the resultant forces of 2 forces found? |
Parallelogram of forces |
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What does U represent? |
Initial velocity |
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What does V represent? |
Final velocity |
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What does A represent? |
Accelleration |
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What does S represent? |
Distance travelled in metres |
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What does T represent? |
Time taken in seconds |
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How fast to objects accellerate toward earth? |
10m.s |
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At the top of an ascent, the veloctiy of an object is? |
0 |
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The trajectory of a ball thrown horizontally is ___ |
parabolic |
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What does a stroboscopic camera do? |
Take LOTS of pictures in a short period of time, think STROBE LIGHT flashing, that's how fast. |
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Give an example of Newton's third law |
When a bullet is fired from a gun, the bullet goes forward but the gun recoils back with force. |
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What does the momentum of an object depend on? |
Velocity and mass |
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What sends microwaves into space? |
A parabolic transmitter |
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What are digital signals used for and why? |
Communication because they attenuate quickly and there's less noise |
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When does the ionosphere reflect radio waves? |
When they have a frequency of under 30MHz, above that they're just scattered and absorbed. |
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What frequencies are used for satellite communication? |
3-30 GHz |
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Where is the ionosphere? |
100km-500km above earth's surface |
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The _______ the size of the gap, the greater the diffraction. |
smaller |
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The larger the size of the gap, the _______ the diffraction |
lesser |
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How is maximum diffraction achieved? |
When the wavelength is the same size as the gap |
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Using the idea of wave pattern, when will sound be loudest coming from 2 speakers? |
When the waves are in sync and the peaks and troughs align- the 2 peaks come together to make a LOUD NOISE yay great woo hoo |
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What's the difference between constructive and destructive interference? |
CON is when the waves are in sync DE is when they're out of sync (replace sync with phase) |
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When does destructive interference occur veruss constructive? |
CON when 2 sources is a whole # wavelengths DE when 2 sources is an odd # wavelengths |
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How does interference between light waves occur? |
When passing through narrow slits |
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What is the wavelength of light? |
0.0004 to 0.0006mm |
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Give an example of a transverse wave |
(anything electromagnetic) |
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Why was Newton's theory of light wrong? |
Because light isn't particles and he's an idiot for thinking so |
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What kind of glasses stop oscillation? |
Polaroid |
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How was Newton's theory of light disproved? |
When we finally measured the speed of light and everyone was like "Ah dude no particles can't travel that fast, Huygens was right..sorry man" |
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What does a plane of unpolarised oscillation look like versus a polarised one? |
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Why does refraction occur? |
Because when light enters a different medium, its speed changes (slows in denser) |
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What indicates the amount of deviation? |
Refractive Index, the greater the deviation, the greater the refractive index. |
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What is dispersion? |
The separation of visible light into its different colors |
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What causes dispersion? |
Each colour slows down by a different amount when entering a new material and speeds up by a different amount when exiting- each has a different angle of refraction |
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What did Snell's Law state? |
sin angle of incidence refractive index= ------------------------------- sin angle of refraction |
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When does total internal reflection occur? |
When the angle of incidence is greater than the critical angle.
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What is the critical angle? |
A 90 degree angle of incidence. |
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What are optical fibres used for? |
-carry telephone calls and computer data as pulses of light -endoscopes to look into bodies |
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Is momentum vector or scalar? |
Vector |
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How do we see things through a camera lens? |
Light from an object passes through the film and the lens to focus on the screen. |
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How does a projector work? |
Light from the bulb passes through the film and the lens to be focused on a screen. |
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How is position/size of an image formed? |
By a convex lens |
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What happens to rays as they pass through a convex lens? |
The one parallel to the principal axis is refracted through the focal point and the one through the centre is not deviated. |
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What is the purpose of a shutter on a camera? |
To open and close allowing light onto film |
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What is the purpose of 'aperture' in camera? |
An adjustable hole allowing different amounts of light onto film |
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Is velocity scalar or vector? |
Scalar |
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What is the job of a condenser lens? |
Make sure film is uniformly illuminated |
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What kind of image is formed by a magnifying glass? |
A virtual one |
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Why can't virtual images be projected onto a screen? |
Because no light passes through them |
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What keeps a satellite in orbit? |
Gravitational force |
