Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    0
    ReputationRep:
    hi guys
    i have 3 questions related to one topic (sounds and waves )

    1: why does bats use ultrasound to catch their prays ?
    >> is it because when they use the ultra sound the pray will not feel or hear that the bat is around or smth like that ??!

    2: why do radio waves are used in radar ??


    3: we have studied in geo many theories about how the earth was build up ? just like THE BIG BANG ! they said that this theory is almost right because we can here the echo of the explosion till NOW!! > and we have studied that sound need a medium to travel so how come we hear the echo of the explosion while it is not possible that the sound travel in space !! ????
    >> idk if i misunderstand it but they didn't mention if the sound that they mean is in earth rather than space .


    thank you .
    • Study Helper
    Online

    21
    ReputationRep:
    Study Helper
    (Original post by nerdholic)
    hi guys
    i have 3 questions related to one topic (sounds and waves )
    Hello and welcome to TSR.

    (Original post by nerdholic)

    1: why does bats use ultrasound to catch their prays ?
    >> is it because when they use the ultra sound the pray will not feel or hear that the bat is around or smth like that ??!
    Bats are nocturnal (night) animals which is a good defensive measure since there are not so many predators around at night which makes them safer at night. They also live in caves which are very dark and so the evolutionary development of echo-location by sound gives them an advantage in both situations. i.e. they cannot use light at night and so use sound instead. High frequencies require smaller vocal tracts to produce the sound and big ears to hear it. Sound is much more directional in the ultrasonic range making it easier to locate things and make a mental image of their surroundings. Humans use eyes which are no use in the dark. Bats use ears which are good in the dark.

    (Original post by nerdholic)

    2: why do radio waves are used in radar ??
    They bounce off metal objects like aeroplanes and are not absorbed/scattered by the atmosphere to the same extent as sound and light.

    (Original post by nerdholic)

    3: we have studied in geo many theories about how the earth was build up ? just like THE BIG BANG ! they said that this theory is almost right because we can here the echo of the explosion till NOW!! > and we have studied that sound need a medium to travel so how come we hear the echo of the explosion while it is not possible that the sound travel in space !! ????
    >> idk if i misunderstand it but they didn't mention if the sound that they mean is in earth rather than space .


    thank you .
    The 'echo' is a figurative way of referring to the Cosmic Microwave Background Radiation (CMBR) which is an electromagnetic wave from the time of the Big Bang (14 billion years ago) and like any other radio wave, but at microwave frequencies. The echo has nothing whatsoever to do with sound!

    Like radio waves, the CMBR-echo can travel through a vacuum.
    Offline

    20
    ReputationRep:
    (Original post by uberteknik)
    Hello and welcome to TSR.



    Bats are nocturnal (night) animals which is a good defensive measure since there are not so many predators around at night which makes them safer at night. They also live in caves which are very dark and so the evolutionary development of echo-location by sound gives them an advantage in both situations. i.e. they cannot use light at night and so use sound instead. High frequencies require smaller vocal tracts to produce the sound and big ears to hear it. Sound is much more directional in the ultrasonic range making it easier to locate things and make a mental image of their surroundings. Humans use eyes which are no use in the dark. Bats use ears which are good in the dark.



    They bounce off metal objects like aeroplanes and are not absorbed/scattered by the atmosphere to the same extent as sound and light.



    The 'echo' is a figurative way of referring to the Cosmic Microwave Background Radiation (CMBR) which is an electromagnetic wave from the time of the Big Bang (14 billion years ago) and like any other radio wave, but at microwave frequencies. The echo has nothing whatsoever to do with sound!

    Like radio waves, the CMBR-echo can travel through a vacuum.
    it's absolutely true that people do (or did) refer to CMBR as the 'echo of the big bang' but there's also something called Baryon Acoustic Oscillation, (BAO) which is to do with actual sound waves in the early universe that got 'frozen' when photons decoupled from baryons. The early universe was good at transmitting sound prior to photon decoupling

    you can detect BAO by doing galaxy surveys with an optical telescope and using stats to look for variations in their distribution - the results tells you something about dark energy.

    BAO is a newer discovery than CMBR, around 10 years, and afaik it's not in school/college syllabi yet - which one he's asking about sort of depends where OP is getting his questions from. Don't mention BAO in answer any exam questions unless you're absolutely sure it's on your syllabus as the person marking you may or may not have heard of it.


    more information on BAO

    http://en.wikipedia.org/wiki/Baryon_...c_oscillations wiki

    https://www.sdss3.org/surveys/boss.php

    http://www.shawprize.org/en/shaw.php...238&fourid=427 (lecture video - 1h+)

    http://astro.dur.ac.uk/~cole/ShawEssay.pdf
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by uberteknik)
    Hello and welcome to TSR.



    Bats are nocturnal (night) animals which is a good defensive measure since there are not so many predators around at night which makes them safer at night. They also live in caves which are very dark and so the evolutionary development of echo-location by sound gives them an advantage in both situations. i.e. they cannot use light at night and so use sound instead. High frequencies require smaller vocal tracts to produce the sound and big ears to hear it. Sound is much more directional in the ultrasonic range making it easier to locate things and make a mental image of their surroundings. Humans use eyes which are no use in the dark. Bats use ears which are good in the dark.



    They bounce off metal objects like aeroplanes and are not absorbed/scattered by the atmosphere to the same extent as sound and light.



    The 'echo' is a figurative way of referring to the Cosmic Microwave Background Radiation (CMBR) which is an electromagnetic wave from the time of the Big Bang (14 billion years ago) and like any other radio wave, but at microwave frequencies. The echo has nothing whatsoever to do with sound!

    Like radio waves, the CMBR-echo can travel through a vacuum.
    (Original post by Joinedup)
    it's absolutely true that people do (or did) refer to CMBR as the 'echo of the big bang' but there's also something called Baryon Acoustic Oscillation, (BAO) which is to do with actual sound waves in the early universe that got 'frozen' when photons decoupled from baryons. The early universe was good at transmitting sound prior to photon decoupling

    you can detect BAO by doing galaxy surveys with an optical telescope and using stats to look for variations in their distribution - the results tells you something about dark energy.

    BAO is a newer discovery than CMBR, around 10 years, and afaik it's not in school/college syllabi yet - which one he's asking about sort of depends where OP is getting his questions from. Don't mention BAO in answer any exam questions unless you're absolutely sure it's on your syllabus as the person marking you may or may not have heard of it.


    more information on BAO

    http://en.wikipedia.org/wiki/Baryon_...c_oscillations wiki

    https://www.sdss3.org/surveys/boss.php

    http://www.shawprize.org/en/shaw.php...238&fourid=427 (lecture video - 1h+)

    http://astro.dur.ac.uk/~cole/ShawEssay.pdf


    thank you both for the information.
    it is totally new for me , i'm going to look for more details about BAO and CMBR .
    thank you again.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you rather give up salt or pepper?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Write a reply...
    Reply
    Hide
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.