Why does sound require a medium for transmission or propagation. But this is not the case with electromagnetic waves. Why?
Why does sound need a medium for transmission whereas the electromagnetic waves doesnt ?
Think of electromagnetic waves as two fields of force, one magnetic and at right angles to this an electric force field. These two fields are created and moving away from their source. They are complete in themselves and do not need to reach a target by influencing anything inbetween the source and target.
The ear responds to pressure waves in the the air. When the air changes from a force the ear detects it as sound. When you clap you affect the air molecules between your hands. These bump into the air molecules all around them and the enrgy is transferred down the line, molecule to molecule to your ear.
By nature sound is force transmitted through a medium to a detector that picks up the change in the medium. EM waves are fields that do not affect the medium but travel through and indpendent of it.
Reply:Sound waves require a medium to travel, because a sound wave is merely a compression that's transmitted through a medium such as air, water, or solid objects like a steel rod.
If you've ever seen a newton's cradle, sound waves are transmitted in much the same way. The compression wave is transmitted by a molecule being thrust forward until it transmits it's momentum into another molecule and so on. That's why there's no sound in a vacuum, there's not enough molecules to transmit the compression of the sound wave, and why the denser an object the faster sound will travel through it.
EM waves are unique and almost magical in a way. They don't need a medium to be transmitted, in fact they move at light speed and are self propogating.
The electrical half generates a magnetic half of a wave, then the magnetic half generates the other electrical half of the electrical wave, which generates the other half of the magnetic wave, and the cycle repeats from there. So with that method EM waves don't require a medium for transmission.
I hope this helps you out.
Reply:This is technically true. Sound requires a medium of transmission to exhibit energy waves. Sound is not energy therefore it needs a medium to be transfered.
Electromagnetic waves require 'Free Space' to propogate energy.
Because 'free space' is always in existence its assumed that electromagnetic waves do not require any other medium to be transferred.
Monday, May 11, 2009
What is considered a medium sized suitcase?
I'm going on a school trip, and the papers they gave us said we are allowed only 1 medium suitcase. My question is; what is considered medium? My suit case is:
H=23 inches
W= 9 inches
L= 18 inches
Is that medium, or is it too large?
I'm packing now, so I need an answer soon!
What is considered a medium sized suitcase?
19-22" is a carry on. 23-26" is medium and 27-30" is really large. Your's sounds just right.
Decent makeup brands
H=23 inches
W= 9 inches
L= 18 inches
Is that medium, or is it too large?
I'm packing now, so I need an answer soon!
What is considered a medium sized suitcase?
19-22" is a carry on. 23-26" is medium and 27-30" is really large. Your's sounds just right.
Decent makeup brands
Why do we use different medium blanks in spectrophotometry?
It's on my lab and I really have no idea. It's not in our packet or anything. I know we use a blank to get it to zero, but I don't know why we need different medium blanks.
Why do we use different medium blanks in spectrophotometry?
your zeroing out the meter so you can take an accurate reading..
say medium 1 is water = it will show up an absorbance on your meter so you use the pure water to zero the machine out so your only reading your sample(water+bacteria for example)
its like your zeroing your scales with a beaker on it... so you can now add things to the beaker and measure it again... and what you will measure is just the substance IN the beaker ... since the weight of the beaker has be removed by zeroing it out in the first place
Why do we use different medium blanks in spectrophotometry?
your zeroing out the meter so you can take an accurate reading..
say medium 1 is water = it will show up an absorbance on your meter so you use the pure water to zero the machine out so your only reading your sample(water+bacteria for example)
its like your zeroing your scales with a beaker on it... so you can now add things to the beaker and measure it again... and what you will measure is just the substance IN the beaker ... since the weight of the beaker has be removed by zeroing it out in the first place
What is the easiest medium to grow microbes in?
ive got a bio project that requires me to culture micobes from my surroundings.what medium would be ideal?preferably something i can find around home,or is easily available.ive heard agar plates are good.how can i prepare them?
What is the easiest medium to grow microbes in?
Make'em yourself agar plates:
Get some flavourless/colourless jello and chichen soup, prepare the chichen soup as indicated but with enough water to make a bowl full of jello, then prepare the flavourless/colourless jello as indicated in the box. That ought to do it. In microbiology labs we call it nutrient agar, but we use molecular grade agar. You decide how solid you want your chicken jello by how much water you add, so if you don't want to have to put it in the fridge to keep it solid, use half as much water as the jello recipe asks for. That ought to keep the jello solid, even at room temp.
What is the easiest medium to grow microbes in?
Make'em yourself agar plates:
Get some flavourless/colourless jello and chichen soup, prepare the chichen soup as indicated but with enough water to make a bowl full of jello, then prepare the flavourless/colourless jello as indicated in the box. That ought to do it. In microbiology labs we call it nutrient agar, but we use molecular grade agar. You decide how solid you want your chicken jello by how much water you add, so if you don't want to have to put it in the fridge to keep it solid, use half as much water as the jello recipe asks for. That ought to keep the jello solid, even at room temp.
What kind of oil medium should i use to make the texture of my paint thick?
Is there a oil medium for this?
What kind of oil medium should i use to make the texture of my paint thick?
Well, most mediums are meant to thin paint that is too thick. I would suggest you put the paints out on your palette and let them sit over night or longer. That will thicken them. Or, try other brands of paint. Some brands are very dry and thick right out of the tube.
Reply:Talens modeling paste is supposed to work for oils as well. Look it up in Dick Blick.
Reply:oil pastel melt it and/or ad water
What kind of oil medium should i use to make the texture of my paint thick?
Well, most mediums are meant to thin paint that is too thick. I would suggest you put the paints out on your palette and let them sit over night or longer. That will thicken them. Or, try other brands of paint. Some brands are very dry and thick right out of the tube.
Reply:Talens modeling paste is supposed to work for oils as well. Look it up in Dick Blick.
Reply:oil pastel melt it and/or ad water
What is the most economical way to access repair information for medium and heavy duty trucks?
I own a small delivery fleet of 5 medium duty trucks. 3 are Peterbilts, 1 is a Freightliner, and one is a Kenworth. Can anyone tell me what the best method is to find repair information on the trucks and their engines? I would like to do my repairs in-house if I can as opposed to outsourcing everything as I have had to do in the past.
What is the most economical way to access repair information for medium and heavy duty trucks?
Library has book and on-line
Reply:Chilton's repair manuals, not cheap, but a lot cheaper than one mechanic's visit.
safety shoes
What is the most economical way to access repair information for medium and heavy duty trucks?
Library has book and on-line
Reply:Chilton's repair manuals, not cheap, but a lot cheaper than one mechanic's visit.
safety shoes
Wednesday, April 29, 2009
What type of medium-sized tree can I plant in my front yard?
I'm looking to plant a medium sized tree in my front yard... preferably one that isn't too expensive. I'd like to plant one that has flowers on it... but nothing too small (as it would look weird with the big trees surrounding it) and nothing too big (because it's being planted in front of our house and I don't want it to cover up the view of our house from the road.)
thanks so much!
What type of medium-sized tree can I plant in my front yard?
If you live in zone 5 or south, (low temps not below say..-10 or -15):
Canadian Redbud (cercis canadensis): beautiful rose colored buds to deep pink blooms, (May),then heart shaped leaves. Dark wood. Usually reaches around 20'.
Flowering Dogwood (cornus florida): beautiful bracts in creamy white or pink,("bloom" is April/May) lots of horizontal branching with an open form and height of around 25 - 30'. This can be artfully pruned.
Korean Dogwood (cornus kousa), similar to the above but somewhat more exaggerated horizontal branching and slightly different bloom time (May/June), blooms are off-white.
Apple (malus domestica) classic and pretty in a sunny location with good drainage. Crab apple trees are nice and some have fragrance. Dwarf/semi dwarf trees can be 6-8', and classic crabapples are usually around 20' high.
Fringe Tree (chionathus) 12-20' high. Blooms white "fringe" in May/June, nice fragrance, and leaves turn golden in fall. This is pretty and different. But it doesn't always bloom right away unless you get one that is already 3 year old nursery stock or better. For best look a single trunk is nicest. It is hardy to zone 4.
Star Magnolia (magnolia stellata) 15-20' high, blooms May/June, fragrant and double. Hardy to zone 4, but sometimes blooms are nipped by frost.
Oriental Cherry (prunus sp) Kwanzan nice tree with a pretty color, 20' high, but somewhat short-lived. The life span is usually 20 years or so.
June Berry (amelanchier laevis or a. arborea) pretty native tree with white blooms early April/Mid April. This is really an all-season beauty with nice fall color. 15-20' high.
Stewartia (pseudodcamellia) This is a beauty and blooms later, in July usually. It reaches 20-near 30'. Pretty bark that is reddish and nice glossy foliage. The fall color of the tree is pretty red-orange or sometimes a bit maroon.
Those would be my top choices for zone 5 on south. Without knowing your geographic location, its hard to choose. But, look those up online, usually by the latin name.
Have a good time. Thanks for planting a tree! Its nice for all of us!
Sometimes Home Depot or even, dread, WM have these trees. But check to be sure that they are not stressed out, (yellowed leaves, suckers at base, root-bound-in-pot, insects). The chain stores usually are short on help needed to properly care for trees and shrubs.
Reply:Magnolia, Red Bud, Dogwood, Flowering Japanese Cherry, and Flowering Crap
Reply:A dogwood tree. Their medium in size and have gorgeous pink or white flowers
Reply:You didn't say where you live-- but the redbud tree is native to the United States-- it is small, has assorted pink blooms and there is a white blooming one.
good luck
Reply:dogwood is pretty and if you go to a home improvement store like home depot or Lowe's they are less expensive.
they are so pretty i like the pink ones
Reply:The deciduous crape myrtle is among the longest blooming trees in existence with flowering periods lasting from 60-120 days. Crapes come in heights as short as 18 in (46 cm) and as tall as 40 ft (12 m). Leaves are alternate and smooth, but leaf size depends on variety. Flowers are borne in summer in big showy clusters and come in white and many shades of pink, purple, lavender and red. The fruits that follow are brown or black. When mature they dry and split releasing disk shaped seeds. Depending on variety, crapes grow as large shrubs or as trees that may be either upright or spreading. Large varieties are very fast growing and can put on several feet in a single growing season. Many types have interesting bark that exfoliates in thin flakes exposing lovely cinnamon or gray inner bark. Crapes tend to produce many suckers that should be removed as they appear if you want to maintain them as trees with distinct trunks. They are enthusiastic reseeders so you may find yourself pulling up baby crapes throughout the summer..
thanks so much!
What type of medium-sized tree can I plant in my front yard?
If you live in zone 5 or south, (low temps not below say..-10 or -15):
Canadian Redbud (cercis canadensis): beautiful rose colored buds to deep pink blooms, (May),then heart shaped leaves. Dark wood. Usually reaches around 20'.
Flowering Dogwood (cornus florida): beautiful bracts in creamy white or pink,("bloom" is April/May) lots of horizontal branching with an open form and height of around 25 - 30'. This can be artfully pruned.
Korean Dogwood (cornus kousa), similar to the above but somewhat more exaggerated horizontal branching and slightly different bloom time (May/June), blooms are off-white.
Apple (malus domestica) classic and pretty in a sunny location with good drainage. Crab apple trees are nice and some have fragrance. Dwarf/semi dwarf trees can be 6-8', and classic crabapples are usually around 20' high.
Fringe Tree (chionathus) 12-20' high. Blooms white "fringe" in May/June, nice fragrance, and leaves turn golden in fall. This is pretty and different. But it doesn't always bloom right away unless you get one that is already 3 year old nursery stock or better. For best look a single trunk is nicest. It is hardy to zone 4.
Star Magnolia (magnolia stellata) 15-20' high, blooms May/June, fragrant and double. Hardy to zone 4, but sometimes blooms are nipped by frost.
Oriental Cherry (prunus sp) Kwanzan nice tree with a pretty color, 20' high, but somewhat short-lived. The life span is usually 20 years or so.
June Berry (amelanchier laevis or a. arborea) pretty native tree with white blooms early April/Mid April. This is really an all-season beauty with nice fall color. 15-20' high.
Stewartia (pseudodcamellia) This is a beauty and blooms later, in July usually. It reaches 20-near 30'. Pretty bark that is reddish and nice glossy foliage. The fall color of the tree is pretty red-orange or sometimes a bit maroon.
Those would be my top choices for zone 5 on south. Without knowing your geographic location, its hard to choose. But, look those up online, usually by the latin name.
Have a good time. Thanks for planting a tree! Its nice for all of us!
Sometimes Home Depot or even, dread, WM have these trees. But check to be sure that they are not stressed out, (yellowed leaves, suckers at base, root-bound-in-pot, insects). The chain stores usually are short on help needed to properly care for trees and shrubs.
Reply:Magnolia, Red Bud, Dogwood, Flowering Japanese Cherry, and Flowering Crap
Reply:A dogwood tree. Their medium in size and have gorgeous pink or white flowers
Reply:You didn't say where you live-- but the redbud tree is native to the United States-- it is small, has assorted pink blooms and there is a white blooming one.
good luck
Reply:dogwood is pretty and if you go to a home improvement store like home depot or Lowe's they are less expensive.
they are so pretty i like the pink ones
Reply:The deciduous crape myrtle is among the longest blooming trees in existence with flowering periods lasting from 60-120 days. Crapes come in heights as short as 18 in (46 cm) and as tall as 40 ft (12 m). Leaves are alternate and smooth, but leaf size depends on variety. Flowers are borne in summer in big showy clusters and come in white and many shades of pink, purple, lavender and red. The fruits that follow are brown or black. When mature they dry and split releasing disk shaped seeds. Depending on variety, crapes grow as large shrubs or as trees that may be either upright or spreading. Large varieties are very fast growing and can put on several feet in a single growing season. Many types have interesting bark that exfoliates in thin flakes exposing lovely cinnamon or gray inner bark. Crapes tend to produce many suckers that should be removed as they appear if you want to maintain them as trees with distinct trunks. They are enthusiastic reseeders so you may find yourself pulling up baby crapes throughout the summer..
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