Ka Nānā ʻana i nā Nalu Transverse a me Longitudinal
He mea koʻikoʻi ka hoʻomaopopo ʻana i ka dinamika nalu ma nā ʻano ʻepekema a me nā ʻenekinia he nui. Ma waena o nā ʻano nalu like ʻole, he mea nui loa nā nalu transverse a me longitudinal. He ʻokoʻa loa kēia mau nalu i ko lākou kuhikuhi oscillation e pili ana i ko lākou kuhikuhi hoʻolaha, e alakaʻi ana i nā noi like ʻole a me nā hanana ma nā kahua like ʻole e like me ka acoustics, electromagnetism, a me ka ʻepekema mea.
1. Nā Wehewehena Kumu
ʻO nā nalu transverse he mau nalu kahi e kū pono ai ka oscillation a i ʻole ka neʻe ʻana o ka medium i ke kuhikuhi o ka laha ʻana o ka nalu. ʻO ka laʻana i ʻōlelo pinepine ʻia he nalu māmā, kahi e oscillate ai nā kahua uila a me nā magnetic i ke kuhikuhi o ka huakaʻi nalu. ʻIke ʻia kekahi hoʻohālikelike o kēlā me kēia lā o nā nalu transverse i nā nalu wai, kahi e lele ai nā mea i luna a i lalo ma luna o ka wai ʻoiai e hele ana ka nalu ma ke kai.
ʻO nā nalu longitudinal, ma ka ʻaoʻao ʻē aʻe, he mau nalu kahi e hana ai ka oscillation a i ʻole ka neʻe ʻana ma ke kuhikuhi like me ka laha ʻana o ka nalu. ʻO kahi laʻana koʻikoʻi o kahi nalu longitudinal he nalu kani i ka lewa. Maanei, hoʻopili a kakaikahi nā ʻāpana o ka medium (nā molekala ea) ma ke kuhikuhi o ka huakaʻi nalu, e hana ana i nā wahi o ke kaomi kiʻekiʻe a me ka haʻahaʻa.
2. Hōʻike Makemakika
ʻO ka mālama makemakika o nā nalu e pili pinepine i nā hana e wehewehe ana i nā oscillations ma luna o ka manawa a me ka hakahaka. No nā nalu ma ke kaula (kahi kumu hoʻohālike maʻamau no nā nalu transverse), hiki ke hōʻike ʻia ka neʻe ʻana \( y(x, t) \) penei:
y(x, t) = A sin(kx – omega t + phi)
kahi ʻo \( A \) ka amplitude (ka neʻe ʻana kiʻekiʻe loa), ʻo \( k \) ka helu nalu, ʻo \( \omega \) ke alapine kihi, ʻo \( x \) ke kūlana, ʻo \( t \) ka manawa, a ʻo \( \phi \) ke kūpaʻa pae.
No nā nalu lōʻihi e like me nā nalu kani, hiki ke wehewehe like ʻia ka neʻe ʻana \(s(x, t) \), akā pili ia i nā kaomi a me nā rarefactions o ka medium:
s(x, t) = A √cos(kx – √omega t + √phi)
Maanei, hōʻike ʻo \(s(x, t) \) i ka neʻe ʻana o nā ʻāpana mai ko lākou kūlana kaulike.
3. Nā Waiwai Mekanika a me ka Māmā o ka Nalu
ʻO ka wikiwiki o ka laha ʻana o ka nalu e pili ana i nā waiwai mechanical o ka medium. No nā nalu transverse ma ke kaula, hāʻawi ʻia ka wikiwiki o ka nalu \( v \) e:
\[ v = \sqrt{\frac{T}{\mu}} \]
kahi ʻo \( T \) ke kaomi ma ke kaula, a ʻo \( \mu \) ka nuipaʻa linear (ka nuipa no ka lōʻihi o ke anakahi) o ke kaula.
No nā nalu lōʻihi e like me ke kani i ka lewa, ua hoʻoholo ʻia ka wikiwiki \( v \) e:
\[ v = \sqrt{\frac{E}{\rho}} \]
kahi ʻo \( E \) ka modulus o ka elasticity (i kapa ʻia hoʻi ʻo bulk modulus no nā wai) a ʻo \( \rho \) ka density o ka medium. No ke kani i ka lewa, hiki ke hōʻike hou ʻia kēia ma ka noʻonoʻo ʻana i nā palena kikoʻī o ka lewa, e like me ke kaomi a me ka mahana.
4. Hoʻākāka a me ka Refraction
Hōʻike nā nalu transverse a me longitudinal i nā ʻano e like me ka reflection a me ka refraction. ʻŌlelo ke kumumanaʻo o ka superposition i ka wā e hui ai ʻelua a ʻoi aku paha mau nalu, ʻo ka neʻe ʻana o ka nalu hopena ka huina o nā neʻe ʻana o kēlā me kēia nalu.
No nā nalu transverse, hana ʻia ka reflection ke pā mai kahi nalu ma kahi palena e kū pono ana i kona kuhikuhi o ka hele ʻana, e hoʻohuli ana i ka nalu a hoʻi i hope ma o ka medium kumu. I ka hoʻohālikelike ʻana, hana ʻia ka refraction ke hele kahi nalu i loko o kahi medium ʻokoʻa ma kahi kihi, e hoʻololi ana i kona wikiwiki a me ka nalu lōʻihi me ka mālama ʻana i kona alapine (frequency). Ua ʻike maikaʻi ʻia kēia kumumanaʻo i nā optics, kahi e kūlou ai nā nalu māmā i ke komo ʻana i nā media moakaka like ʻole.
ʻO nā nalu longitudinal e like me ke kani e hōʻike a refract pū kekahi. ʻO nā leo he laʻana pololei o ka hoʻohuli ʻana o nā nalu kani, ʻoiai hiki ke ʻike ʻia ke ʻano o ka refraction i ka wā e neʻe ai nā nalu kani ma waena o nā papa ea o nā mahana like ʻole, e kūlou ana i ko lākou ala ma muli o ka loli o ka wikiwiki o ka nalu me ka mahana.
5. Ke komo ʻana o ka nalu a me ka hoʻokūkū nui ʻana
ʻO ke komo ʻana he hanana kahi e hui pū ai nā nalu ʻelua e hana i kahi nalu hopena o ka amplitude nui aʻe, haʻahaʻa, a i ʻole like. ʻElua ʻano o ke komo ʻana: kūkulu a me ka luku. Hana ʻia ke komo ʻana kūkulu i ka wā e hui pū ai nā nalu e hana i kahi nalu me ka amplitude nui aʻe, a hana ʻia ke komo ʻana luku i ka wā e hui pū ai nā nalu e hopena i kahi nalu me ka amplitude i hoʻemi ʻia a hoʻopau ʻia paha.
No nā nalu transverse, e like me nā nalu wai a i ʻole nā nalu electromagnetic, hiki i nā ʻano hoʻopilikia ke ʻike maka ʻia, e like me ka mea i ʻike ʻia ma nā palena hoʻopilikia i nā hoʻokolohua optical. No nā nalu longitudinal, hiki i nā hanana hoʻopilikia ke hopena i nā kuʻi lohe ʻia, ʻo ia hoʻi nā ʻano like ʻole o ka leo nui ma muli o ka superposition o nā nalu kani o nā alapine like.
6. Hoʻololi i ka ikehu
Hoʻoili nā ʻano nalu ʻelua i ka ikehu ma o ka waena. No nā nalu transverse, hoʻoili ʻia ka ikehu i ke kuhikuhi o ka huakaʻi nalu, i ʻike pinepine ʻia ma o ka neʻe ʻana o nā mea ma luna o ka ʻili o nā nalu wai. Hoʻoili nā nalu longitudinal i ka ikehu ma ke kuhikuhi o ka laha ʻana o ka nalu. I ke ʻano o nā nalu kani, hoʻoili ʻia ka ikehu ma o nā kaomi a me nā kaʻawale ʻana o nā ʻāpana ea, e hoʻoneʻe ana i ka ikehu kani mai ke kumu a i ka mea hoʻolohe.
7. Nā noi hana
Nā Nalu ʻĀwiliwili:
– Nā Nalu Electromagnetic: Hoʻohana ʻia i nā ʻōnaehana kamaʻilio, mai nā nalu lekiō a i nā kukuna gamma.
– Nā Nalu-S Seismic: Kōkua i nā kānaka ʻepekema honua e hoʻomaopopo i loko o ka Honua; He transverse nā nalu-S a ʻaʻole hele i loko o nā wai, e hāʻawi ana i nā hōʻailona e pili ana i ka ʻiwi o ka Honua.
– Nā Mea kani kaula: ʻO nā mea kani e like me nā guitar a me nā violins e hana i ke kani ma o nā kaula haʻalulu e hana ana i nā nalu transverse.
Nā Nalu Longitudinal:
– Acoustics: He mea nui i ka hoʻolaha ʻana o nā nalu kani no ke kamaʻilio ʻana, ke mele, a me ka ʻenehana sonar.
– Kiʻi Lapaʻau: Hoʻohana ka Ultrasound i nā nalu longitudinal e hana i nā kiʻi o nā ʻano o loko o ke kino.
– Nā Nalu-P o ka ʻŌlaʻi: Hele nā nalu seismic longitudinal (Nā nalu-P) ma ka Honua, e hāʻawi ana i ka ʻike koʻikoʻi e pili ana i kona haku mele a me kona ʻano.
Panina
ʻO ke aʻo ʻana i nā nalu transverse a me longitudinal ke kumu o nā ʻano ʻepekema like ʻole. ʻO ko lākou mau ʻano a me nā ʻano like ʻole e hiki ai ke hoʻohana i nā ʻano noi like ʻole, mai nā hana hou ʻenehana a hiki i ka noiʻi ʻepekema kumu. ʻO ka hoʻomaopopo ʻana i kēia mau ʻano nalu e hāʻawi i ka ʻike i nā hanana kūlohelohe, kōkua i ka holomua ʻenehana, a hoʻonui i ko mākou ʻike i ke ao kino.
