Explanation:
Like all EM waves, light transports energy across space. The intensity (energy per unit area and unit time) is proportional to the square of the amplitude of the electric field of the light wave. This energy, however, arrives at a receiver not continuously but in discrete units called photons. The energy transported by an electromagnetic wave is not continuously distributed over the wave front. It is transported in discrete packages. Photons are the particles of light.
Properties of photons:
Photons always move with the speed of light.
Photons are electrically neutral.
Photons have no mass, but they have energy E = hf = hc/λ. Here h = 6.626*10-34 Js is a universal constant called Planck's constant. The energy of each photon is inversely proportional to the wavelength of the associated EM wave. The shorter the wavelength, the more energetic is the photon, the longer the wavelength, the less energetic is the photon.
A laser beam and a microwave beam can carry the same amount of energy. In this case the laser beam contains a smaller number of photons, but each photon in the laser beam has a higher energy than the photons in the microwave beam.
Photons can be created and destroyed. When a source emits EM waves, photons are created. When photons encounter matter, they may be absorbed and transfer their energy to the atoms and molecules. Creation and destruction of photons must conserve energy and momentum. The magnitude of the momentum of a photon is p = hf/c = h/λ.
Problem:
What is the energy of a photon of blue light (λ = 450 nm) and of a photon of red light (λ = 700 nm) in units of eV = 1.6*10-19 J?
Solution:
E = hc/λ.
Blue light: E = (6.626*10-34 Js)(3*108 m/s)/(450*10-9 m) = 4.4*10-19 J = 2.76 eV
Red light: E = (6.626*10-34 Js)(3*108 m/s)/(700*10-9 m) = 2.8*10-19 J = 1.8 eV
Problem:
A 100-W incandescent light bulb uses 100 W (100 W = 100 J/s) of electrical power but only radiates about 15 W of actual visible light. Roughly how many visible photons per second hit the open pages of a typical hardcover book if the pages are about 2 m from the bulb and face it directly?
Solution:
We have to make a variety of estimations and approximations to solve this problem.
To find the number of photons hitting the pages each second, we have to know the light energy hitting the pages per second and the energy per photon. We could compute the latter if we knew the wavelength of the light, but the visible light emitted by a normal incandescent bulb is a mix of wavelengths.
Let us estimate that the average wavelength of the visible light is about 550 nm, which is in the yellow region of the spectrum. This means that the average energy per photon is about
E = hc/λ = (6.626*10-34 Js)(3*108 m/s)/(550*10-9 m) = 3.61*10-19 J = 2.26 eV.
To find the number of photons hitting the pages of a book, we need to know the energy per second that falls on the pages. Let us assume that the light energy from the bulb travels uniformly in all directions. Imagine a sphere centered on the light bulb with a radius R = 2 m. Every second, 15 J or so of visible light energy crosses this sphere. If the light energy is spread uniformly over the sphere, then the intensity of the visible light or the energy per unit area per unit time in units of W/m2 at any point on the inner surface of the sphere will be
I = Plamp/(4πR2),
Electrons are ejected from a metal surface with speeds ranging up to 4.6*105 m/s when light with a wavelength of 625 nm is used.
(a) What is the work function of the surface?
(b) What is the cutoff frequency of the surface?
Athlete’s foot is a fungus that attacks the area between the toes and sometimes the sole of the foot, causing redness, irritation, and a scaly look to the skin. It may even invade the area under the toenails. The fungus thrives in damp, warm places, such as shower rooms, swimming pools, and gymnasiums.
a.) Mutualism
b.) Commensalism
c.) Parasitism
d.) Predator-Prey
Answer:
Parasitism
Explanation:
What's the difference between the "matter that makes up wood" and the "matter that makes up water"? Explain your ideas in full sentences.
They describe different forms of matter, solid and liquid. As well as both being entirely differently structured forms of matter.
They distinguish between solid and liquid matter. In addition to being completely different types of matter.
What is matter?Matter is defined as everything that takes up space other words, the "material" that makes up the universe.
All matter is composed of substances known as elements, each of which has unique chemical and physical properties and cannot be decomposed into other materials through ordinary chemical reactions.
Atoms and molecules make up some of the material in the category of solids, liquids, and gases.
The matter that makes up wood have characteristics of any solid, i.e., high intermolecular force of attraction that holds it shape.
The matter that is making water will have liquid characteristics, which do not have a particular shape and will have weak intermolecular forces of attraction.
Thus, this is the chief difference between the "matter that makes up wood" and the "matter that makes up water".
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which of the following is a change of state of a substance?
Answer:
C
Explanation:
Water which is a liquid becomes ice which is a solid
That would be C, due to the fact that the water changes from a liquid to a solid. (I hope that helped ^^)
An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could pick up was measured. What's the independent variable and dependent variable?
Answer:
Independent variable: SIZE OF NAILS
Dependent variable: NUMBER OF PAPER CLIPS
Explanation:
The independent variable in an experiment is the variable that is changed or manipulated by the experimenter in order to effect a measurable response. In this investigation, the DIFFERENT SIZES OF NAILS USED is the INDEPENDENT VARIABLE.
The dependent variable is the variable that is measured in the experiment. It is the variable that responds to changes made to the independent variable. In this investigation, THE NUMBER OF PAPER CLIPS the electromagnet could pick up is the DEPENDENT VARIABLE.
The dependent variable is the number of paper clips that the electromagnet could pick up while the independent variable is sizes of nail used.
An experiment consists of;
a dependent variable and an independent variable.The independent variable is the variable that is being manipulated while the dependent variable changes with changes in the independent variable.
In this experiment, the dependent variable is the number of paper clips that the electromagnet could pick up while the independent variable is sizes of nail used.
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what are two pure substances that whould make a mixure and could then be separated from the mixure with a magnet
Answer:
We can separate iron from a mixture of sand and iron, as only the iron is attracted to the magnet.
Explanation:
9.
Which of the following best describes the term VACUUM?
A. A vibration moving energy from place to place.
B. The part of a wave that is pushed together.
C. Empty Space
D. The material through which a mechanical wave can travel.
Answer:
C. Empty Space
Explanation:
A vacuum is an empty space.
In a vacuum, there is no form of matter present. A vibration moving energy from place to place is a waveThe part of a wave pushed together is called a compressionThe material through which a mechanical wave can travel is a mediumSo, a vacuum is simply an empty space devoid of matter.
What is found between the monomers on the different strands of DNA
Phosphodiester bonds found between the monomers on the different strands of DNA.
What is DNA ?Deoxyribonucleic acid is called as DNA. The molecule found inside cells that carry the genetic material necessary for an organism to develop and function. This knowledge can be passed on from one generation to the next thanks to DNA molecules.
The information molecule is DNA. It contains information needed to create proteins, which are other big molecules.
In DNA polymers, phosphodiester bonds link the 5' carbon of one nucleotide and the 3' carbon of another nucleotide. In a DNA polymer, phosphodiester bonds strong electromagnetic attractants join the nucleotide monomers together.
Thus, Phosphodiester bonds found between the monomers on the different strands of DNA.
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When a liquid freezes into a solid, the particles of the substance:
A.Lose energy
B.Gain energy
C.Move faster
D.Disappear
Answer:
(see below)
Explanation:
Using process of elimination:
A) lose energy
When a liquid freezes into a solid, the particles move a lot slower because the once-flowing particles are now about to be stuck in place, barely vibrating in its structure.
So, yes, they has lost energy, but there can be a better answer.
B) gain energy
When a liquid freezes into a solid, the particles move a lot slower, so there is no way there is more energy now. If there was to be more energy, it would be a gas now.
So, no, they did not gain energy.
C) move faster
When a liquid freezes into a solid, the particles move a lot slower, so there is no way they're moving faster now. Otherwise it would be a gas now.
So, no, they did not move faster.
D) disappear
Particles of a substance don't just . . . disappear. There is no way matter can be destroyed or created, only changed in form, according to the Conservation of Matter.
So, no, they did not disappear.
So the answer is most likely A.
The movement overall of molecules from regions of high concentration to regions of low concentration is called _______.
a.diffusion
b.osmosis
c.concentration
Answer:
diffusion is the answer
Explanation:
Why does an ionic bond have a high melting point?
A. Very little energy is required to overcome the repulsive forces that hold the ionic crystal together.
B. A lot of energy is required to overcome the attractive forces that hold the ionic crystal together.
C. A lot of energy is required to overcome the repulsive forces that hold the ionic crystal together.
D. Very little energy is required to overcome the attractive forces that hold the ionic crystal together.
Answer:
B
Explanation:
i just take the test
An ionic bond has a high melting point because a lot of energy is required to overcome the attractive forces that hold the ionic crystal together. The correct option is B.
In an ionic bond, atoms transfer electrons to form positively charged cations and negatively charged anions. These oppositely charged ions are attracted to each other, creating strong electrostatic forces between them.
When a solid ionic compound is heated, the thermal energy increases, causing the ions to vibrate more vigorously. As the temperature continues to rise, the ions gain enough energy to break free from their fixed positions within the crystal lattice. This requires a lot of energy because the attractive forces between the ions are strong and must be overcome.
Thus, the correct option is B.
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which of the folllowing is NOT a mixture?
A. table salt
B. lemonade
C. garden soil
D. salad dressing
Jen is walking her dog at a constant rate.
They keep a constant rate as they turn a
corner. Why has their velocity changed?
Answer:
4is the answer
Explanation:
Joelle is a manager at a construction company, and she is interested in the chemistry behind the materials they use. She has begun studying the materials used to fill walls. She knows that to keep the temperature inside a room steady the material must be a thermal insulator, and she predicts that materials should not be acidic or else they would dissolve too easily in water.
Which of these is a molecular ingredient that could be used in a wall-filling material ?
C6H6
Na6Ba6
NeNa
HCl
Answer:
C6H6
Explanation:
Now let us take a recap of Joelle's criteria for a wall filling material;
1) the material must be a thermal insulator
2) materials should not be acidic
3) they will not dissolve too easily in water.
If we consider the options provided, Na6Ba6 and NeNa do not exist. HCl is an acid and does not match Joelle's criteria. Hence the answer must be C6H6.
Answer:
A
Explanation:
A is glossy and ductile. A is used as a conductor of electricity.
Which of the following is the best description of A?
Answer:
It is a metal
Explanation:
please help me out with this!!
Answer:
C?
Explanation:
HELP ME PLEASEEEEEEE!?!?!?!!
Answer:
amps is how hard it is for the volts to get through hope this helped
Explanation:
Which parts do all cells have in common?
a Golgi apparatus
b mitochondria
C ribosomes
d nucleus
Answer:
a Golgi apparatusExplanation:
1) Sarah's family raises chickens,
They buy 15 pounds of feed per
week. If chickens eat all but 4
pounds, how many ounces of
feed did they eat?
Answer:
hhdbnahdhs
Explanation:
hajsbbdjsod
A teacher placed a plastic cup of warm coffee with a lid in the freezer.
Which statement describes the frozen coffee in comparison with the warm coffee?
A. The arrangement of the coffee molecules in the same
B. The temperature of the coffee has increased
C. The amount of coffee in the same
D. The speed of the coffee molecules has increased
Answer:
C. The amount of coffee is the same.
Explanation:
Verified
What is a chemical reaction?
Oь
A chemical reaction happens only under special circumstances.
A chemical reaction is when the bonds of one substance form and then break which makes something different.
A chemical reaction has infinite possiblities to happen.
A chemical reaction is when the bonds of one substance break and form new bonds to make something different.
ос
Od
Answer:
a process that involves rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction
What is the funtion of an atomic atom?
Forces and Motion:Question 1
Acceleration is the rate of change in an object's...
Select one:
force.
gravity.
ооо
velocity
mass.
Answer:
velocity
Explanation:
Acceleration is the rate of change of velocity with time.
Acceleration= velocity/time
The type of bonding depicted below is most likely:
Answer:
C Ionic
Explanation:
Can someone help me put this in my ‘own’ words please ?
Answer:
I think this should help
Photosynthesis happens when the sun and carbon dixoxide come together in the plant and a chemical reaction happen that make a suger thats called glucose
Explanation:
Based on these drawings, which element is the least reactive?
Answer:
youre not showing a drawing. look at the table. electronegativity trend is “down” and “right”. you should get your answer by looking at that trend. the more electronegative, the more reactive.
help on this question please
An EMR photon is transmitted by as a 100 MHz FM radio wave. What is it’s A) wavelength B) energy of one photon C) Total energy of 1x10^18 photons?
A. λ = 3 m
B. E = 1.9878 x 10⁻³³ J
C. Total energy : 1.9878 x 10⁻²⁰ J
Further explanationThe photoelectric effect is an electron coming out of a metal because of electromagnetic radiation
One type of electromagnetic radiation is light
Radiation energy is absorbed by photons
The energy in one photon can be formulated as
[tex]\large{\boxed{\bold{E\:=\:h\:.\:f}}}[/tex]
Where
h = Planck's constant (6,626.10⁻³⁴ Js)
f = Frequency of electromagnetic waves
f = c / λ
c = speed of light
= 3.10⁸
λ = wavelength
A. wavelength
[tex]\tt \lambda=\dfrac{c}{f}\\\\\lambda=\dfrac{3.10^8}{1.10^8~Hz}=3~m[/tex]
B. energy of one photon
[tex]\tt E=h\times f\\\\E=6.626\times 10^{-34}\times 3=1.9878\times 10^{-33}~J[/tex]
C. Total energy
[tex]\tt 1.9878\times 10^{-33}\times 10^{18}=1.9878\times 10^{-20}[/tex]
In the interactive, start adding neutrons to the nucleus.
What happens to the mass number each time you add a neutron, and why?
Answer:
Explanation:
Each time you add a neutron, it adds one mass number to the mass because each neutron and proton weighs approximately 1 amu.
Answer:
The mass increases
Explanation:
When protons and neutrons are added, the mass increases. Electrons, on the other hand, are so small they do not affect the mass.
2NaOH + H2SO4 → Na2SO4 + 2H20
(What reaction would occur)
which statement describes the pattern in the density of gases in the atmosphere
Answer:They are less dense near the top of the atmosphere.
Explanation: