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Flashcards in P5 Deck (40):

How does a satellite stay in orbit above earth?

They are pulled toward Earth by the force of gravity thus they are constantly falling but they also have a velocity at right angle to this fall and thus the resultant force of motion which is in a diagonal direction- this is the centripetal force

This happens at every point in the orbit so it changes direction constantly and accelerated in a circular path around the planet but at the same height


Describe how a geostationary satellite works?

They orbit high above the earth at around 36 000km so lower gravitational force and slower speed and so have an orbital period of 24 hours

They staying above the same position over the earth all the time - orbiting above the equator

It needs centripetal force provided by gravity to move in circular motion


Describe how a low polar satellite works?

It orbits closer to earth (340km) so gravitational force stronger and so has a shorter orbital period- around 90 minutes because it gas FASTER speed

As the Earth rotates, the satellite can observe any part of the planet over a few days

Goes over the poles


What are the uses of geostationary and low polar satellites?

- Geostationary used for TV and mobile phone signals
- used for weather mapping and forecasting

- Low polar creates clearer images because closer
- Needs less powerful communication tech
- Military uses- spying


What equation should you use if the object travels in a straight line and at a constant acceleration?

v = u + at

s = ut + 1/2at2

v2 = u2 + 2as


What is the name of the shape of the trajectory of a projectile?



Describe a projectile's motion in terms of its speed and acceleration

- Its horizontal velocity stays the same throughout because air resistance is ignored and the only force acting on it was the initial kick

- No horizontal acceleration

- Its vertical velocity increases steadily as it falls because gravity accelerates it at a rate of 10m/s2

- Creates a resultant vector- the resultant velocity- the ever increasing downward velocity
- Air resistance would decrease horizontal velocity if considered


What is Newton's third law?

Every action has an equal and opposite reaction
- equal and opposite force is exerted


When a crane holds a load, describe the forces involving this

The load pulls the crane down and crane pull sup with equal and opposite force

The earth attracts the load/crane to the ground and the crane/load attracts the earth to it


What is done to increase the quality of the signal?

Dishes with size much bigger than the wavelength is used

They reflect the signal into the central receiver to be processed by TV


What is a terrestrial signal?

Microwave signals sent from local transmitter


What kind of signal frequencies are used to communicate with nearby satellites?

Low frequencies


What kind of signal frequencies are used to communicate with distant satellites?

High frequencies


Why does satellite communication use digital signals?

Because any interference can then be easily removed


Why do long radio waves have a large range?

Because they have a low frequency so they are reflected off the ionosphere and travel out of line of sight


Why do radiowaves diffract better?

Because they have longer wavelengths and the longer the wavelength, the bigger the diffraction


How are interference patterns caused?

They are caused by the waves travelling different distances- called the path difference


What produces constructive interference?

If 2 waves of similar frequencies coincide in phase they will superimpose the wave energy and produce a wave with double the amplitude

The path difference must be an even number of half wavelengths


What produces destructive interference?

If two waves are exactly out of phase they will cause a wave of 0 amplitude

The path difference must be an odd number of half wavelengths


What is AM?

Amplitude modulation

Changing the amplitude of the carrier wave as it changes on the original signal


Who are the 2 scientists involved in the development of the light model?

Christiaan Huygens

Sir Isaac Newton


What did Newton say about light?

That it was a particle rather than wave because otherwise it would diffract but in shadows there is a clear edge

It would otherwise spread out but light travels in straight lines


How was Newton's light model proved to be wrong?

Waves were made to diffract using a small slit the same size as the wavelength

It forms an interference pattern as light waves do

It was also polarised showing that It is not only a wave but a transverse wave


What is polarisation?

It only happens in transverse waves

It uses a filter to make the vibrations of the light only move in one plane because there are filters in different directions preventing the light to move this way

It can use a Polaroid filter to do this


What affects the refractive index of a material?

- The more slowly light travels through that material
- The denser the material

....the higher the refractive index

- The shorter the wavelength of the light the slower it travels in the medium thus the greater the refractive index


Materials with a higher refractive index causes the light to ...

...slow down more and bend towards the norm


When light enters a denser medium...

... it slows down, wavelength reduces,

Both speed and wavelength return to normal once it exits the medium`


What are the two conditions needed for total internal reflection?

- It must be in the more optically denser material
- Angle of incidence must be higher than the critical angle


How does refractive index affect critical angle?

The bigger the refractive index, the smaller the critical angle


Give some uses of TIR

Cats' eyes TIR the car's headlight to show where the road markings far ahead of them

Optical fibres to send info/ endoscope

Binoculars and telescopes


The fatter the convex lens...

... the shorter the focal length because it refracts more


Light hitting the lens parallel to the principle axis will...

... refract and go through the principle focus


Light hitting the lens at an angle to the principle axis after diverging from a focus will...

... travel out of the lens a parallel to principle axis


Light passing through the optical centre will...

... continue to travel in the same direction


What kind of images form from a projector?

It will form an inverted image that is real- meaning it will form on a screen when focused

If the object is close to the lens, it will be a larger image
if object is far away, it will form smaller image than size of object


What kind of images do magnifying glasses produce?

It forms a virtual image that is the right way up


What parts of the electromagnetic spectrum cannot pass through the atmosphere?

The higher energy waves such as gamma


What frequency of radio waves are reflected by atmosphere and what pass through?

less than 30MHz be reflected but more than this and it will pass through


How are signals passed between satellites?

As digital signals: pulses of microwaves


How does the gravity affect the vertical acceleration and velocity of a rocket as it rises?

The vertical acceleration stays constant

The velocity decreases