# This from efexvel physics sample assesment paper 2018 October

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Thread starter 1 year ago
#1
https://i.imgur.com/FszhkNB.jpg

What does pulse duration mean here?and secondly the calculated distance (which is about 225 meters ) is less than the distance of the aircraft from the airport (which is 60km) but the marks scheme says that the pulse duration is suitable to detect the aircraft at 60km,how?
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1 year ago
#2
(Original post by riamu)
https://i.imgur.com/FszhkNB.jpg

What does pulse duration mean here?and secondly the calculated distance (which is about 225 meters ) is less than the distance of the aircraft from the airport (which is 60km) but the marks scheme says that the pulse duration is suitable to detect the aircraft at 60km,how?
I'll guess it's a question about radar; a system of direction and range finding based on reflecting radio waves off aircraft and other radio reflective objects.

pulse duration might be the duration of the pulses of radio energy being transmitted by the radar station and if so the significance is perhaps that the station can't 'listen' for the beginning of the return pulse until it's finished transmitting the end of the transmitted pulse.

The radio wave will travel through air at 300,000 km/s meaning it will travel one millionth of that distance in 1 μs
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Thread starter 1 year ago
#3
(Original post by Joinedup)
I'll guess it's a question about radar; a system of direction and range finding based on reflecting radio waves off aircraft and other radio reflective objects.

pulse duration might be the duration of the pulses of radio energy being transmitted by the radar station and if so the significance is perhaps that the station can't 'listen' for the beginning of the return pulse until it's finished transmitting the end of the transmitted pulse.

The radio wave will travel through air at 300,000 km/s meaning it will travel one millionth of that distance in 1 μs
but i dont get it that the distance that the radar can measure in 1.5 micro seconds is way less than the distance the aircraft is from the radar so how can it then detect it when its not in its range?
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1 year ago
#4
That's a minimum round trip distance. Pulses of that duration are suitable for detecting aircraft at distances greater than half the minimum you calculated. Half because the pulses are making a 2 way trip radar to aircraft and back to radar.

The question might be driving at something else but you haven't shown the full question yet so I can't tell.
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Thread starter 1 year ago
#5
(Original post by Joinedup)
That's a minimum round trip distance. Pulses of that duration are suitable for detecting aircraft at distances greater than half the minimum you calculated. Half because the pulses are making a 2 way trip radar to aircraft and back to radar.

The question might be driving at something else but you haven't shown the full question yet so I can't tell.
https://qualifications.pearson.com/c...ysics-SAMs.pdf

heres the link -it will take you to the sample assesment paper and know that its unit 2 question no;11
i really need help with this
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1 year ago
#6
it's a 3 pointer so I'd suggest

state the problem with the antenna being unable to receive and transmit at the same instant
calculate the distance between the front and back of the pulse
compare that to the round trip distance it's required to travel between the antenna and the aircraft and draw a conclusion about the suitability of that pulse length
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