# physics

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#1
can someone explain the 16th question in the physics unit 2 January 2010 edexcel paper?
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6 years ago
#2
Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there. You can also find the Exam Thread list for A-levels here and GCSE here. Just quoting in Puddles the Monkey so she can move the thread if needed Spoiler:
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(Original post by Puddles the Monkey)
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6 years ago
#3
Would it be possible to post the question here? i dont see a 2nd of january paper for edexcel unit 2.
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6 years ago
#4
This one? In 1921, Albert Einstein won the Nobel Prize for his work on the photoelectric effect.The results of experiments on the photoelectric effect show that:
• photoelectrons are not released when the incident radiation is below a certain threshold frequency;
• the kinetic energy of the photoelectrons released depends on the frequency of theincident light and not its intensity.
Explain how these results support a particle theory, but not a wave theory of light. (6m)
Spoiler:
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Photoelectrons aren't released when the incident radiation is below a certain threshold frequency.
This supports a particle theory because a photon can have a certain amount of energy (depending on its frequency, because E=hf).
To release an electron, you need a certain amount of energy (equal to or above the work function for that material).
One photon causes the release of one electron as long as it has a high enough energy, and any "extra" energy above the work function becomes KE of the electron.

The kinetic energy of the photoelectrons released depends on the frequency of the incident light and not its intensity.
This supports a particle theory because it goes against wave theory.
Wave theory would suggest that energy is spread over the whole wave (and that energy depends on its intensity). So if an electron is exposed to a wave for a long time, it should gain energy over this time and eventually get released. However, this doesn't happen.

In fact, a higher intensity only means that there are more photons per unit area, but you only need one photon per electron. Its intensity doesn't matter if the individual photons don't have a high enough frequency and energy.

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#5
can someone explain the following questions from edexcel physics January 2014 unit 2 IAL paper
16th question (b)
17th qustion
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#6
(Original post by Laurasaur)
This one? In 1921, Albert Einstein won the Nobel Prize for his work on the photoelectric effect.The results of experiments on the photoelectric effect show that:
• photoelectrons are not released when the incident radiation is below a certain threshold frequency;
• the kinetic energy of the photoelectrons released depends on the frequency of theincident light and not its intensity.
Explain how these results support a particle theory, but not a wave theory of light. (6m)

Spoiler:
Show
Photoelectrons aren't released when the incident radiation is below a certain threshold frequency.
This supports a particle theory because a photon can have a certain amount of energy (depending on its frequency, because E=hf).
To release an electron, you need a certain amount of energy (equal to or above the work function for that material).
One photon causes the release of one electron as long as it has a high enough energy, and any "extra" energy above the work function becomes KE of the electron.

The kinetic energy of the photoelectrons released depends on the frequency of the incident light and not its intensity.
This supports a particle theory because it goes against wave theory.
Wave theory would suggest that energy is spread over the whole wave (and that energy depends on its intensity). So if an electron is exposed to a wave for a long time, it should gain energy over this time and eventually get released. However, this doesn't happen.

In fact, a higher intensity only means that there are more photons per unit area, but you only need one photon per electron. Its intensity doesn't matter if the individual photons don't have a high enough frequency and energy.

thank you
0
6 years ago
#7
(Original post by kritz20)
can someone explain the following questions from edexcel physics January 2014 unit 2 IAL paper16th question (b)17th qustion

An energy level is a discrete quanta of energy for an electron in the atom. An electron can only have discrete energy levels within the atom.
When an electron attains energy (usually from radiation) it moves up energy levels. When it drops back down, the exact amount of energy that was used to take the electron up to the new energy level is released in the form of a photon. This energy released is equal to the energy difference between the shells in eV (electronvolts).

You can then use to get in joules, where .
This photon has where is the energy, is plancks constant and is the frequency of the photon.

In this question: for energy difference between shells    Question 17:
The incident light has a stream of photons. These photons cause the photoelectric effect on the metal, liberating photoelectrons from the surface.

This photon from the incident ray has energy The liberation only occurs if which is the work function of the metal (minimum energy required for a photon to liberate an electron is the work function of a material)

The photoelectron has energy The kinetic energy is a maximum as some energy may be transferred to the metal itself, i.e some energy from the photon is transferred to the surroundings.
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#8
(Original post by The-Spartan)
An energy level is a discrete quanta of energy for an electron in the atom. An electron can only have discrete energy levels within the atom.
When an electron attains energy (usually from radiation) it moves up energy levels. When it drops back down, the exact amount of energy that was used to take the electron up to the new energy level is released in the form of a photon. This energy released is equal to the energy difference between the shells in eV (electronvolts).

You can then use to get in joules, where .
This photon has where is the energy, is plancks constant and is the frequency of the photon.

In this question: for energy difference between shells    Question 17:
The incident light has a stream of photons. These photons cause the photoelectric effect on the metal, liberating photoelectrons from the surface.

This photon from the incident ray has energy The liberation only occurs if which is the work function of the metal (minimum energy required for a photon to liberate an electron is the work function of a material)

The photoelectron has energy The kinetic energy is a maximum as some energy may be transferred to the metal itself, i.e some energy from the photon is transferred to the surroundings.
thank youuu
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#9
can someone explain the 21st question part (b) and (c) from edexcel physics june 2015 (IAL) unit 2 paper?
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#10
can someone explain the 11th question in edexcel physics January 2015 unit 2 paper?
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#11
can someone explain the 11th question in edexcel physics January 2015 unit 2 paper?
0
#12
Can someone explain the 14th question part (a) inedexcel physics January 2015 unit 2?
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#13
Can someone explain the 13th question part (b) inedexcel physics January 2015 unit 2?
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#14
Can someone explain the 15th question part (b) inedexcel physics January 2015 unit 2?
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#15
(Original post by Laurasaur)
This one? In 1921, Albert Einstein won the Nobel Prize for his work on the photoelectric effect.The results of experiments on the photoelectric effect show that:
• photoelectrons are not released when the incident radiation is below a certain threshold frequency;
• the kinetic energy of the photoelectrons released depends on the frequency of theincident light and not its intensity.
Explain how these results support a particle theory, but not a wave theory of light. (6m)

Spoiler:
Show
Photoelectrons aren't released when the incident radiation is below a certain threshold frequency.
This supports a particle theory because a photon can have a certain amount of energy (depending on its frequency, because E=hf).
To release an electron, you need a certain amount of energy (equal to or above the work function for that material).
One photon causes the release of one electron as long as it has a high enough energy, and any "extra" energy above the work function becomes KE of the electron.

The kinetic energy of the photoelectrons released depends on the frequency of the incident light and not its intensity.
This supports a particle theory because it goes against wave theory.
Wave theory would suggest that energy is spread over the whole wave (and that energy depends on its intensity). So if an electron is exposed to a wave for a long time, it should gain energy over this time and eventually get released. However, this doesn't happen.

In fact, a higher intensity only means that there are more photons per unit area, but you only need one photon per electron. Its intensity doesn't matter if the individual photons don't have a high enough frequency and energy.

Can u explain the 11th question and the 20thquestion in edexcel physics june 2014 (IAL) unit 2 paper. I do not understandthe answer given in the marking scheme. I have mock exams next week and I needhelp
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#16
(Original post by The-Spartan)
An energy level is a discrete quanta of energy for an electron in the atom. An electron can only have discrete energy levels within the atom.
When an electron attains energy (usually from radiation) it moves up energy levels. When it drops back down, the exact amount of energy that was used to take the electron up to the new energy level is released in the form of a photon. This energy released is equal to the energy difference between the shells in eV (electronvolts).

You can then use to get in joules, where .
This photon has where is the energy, is plancks constant and is the frequency of the photon.

In this question: for energy difference between shells    Question 17:
The incident light has a stream of photons. These photons cause the photoelectric effect on the metal, liberating photoelectrons from the surface.

This photon from the incident ray has energy The liberation only occurs if which is the work function of the metal (minimum energy required for a photon to liberate an electron is the work function of a material)

The photoelectron has energy The kinetic energy is a maximum as some energy may be transferred to the metal itself, i.e some energy from the photon is transferred to the surroundings.
Can you explain the 11th question and the 20thquestion in edexcel physics june 2014 (IAL) unit 2 paper. I do not understandthe answer given in the marking scheme. I have mock exams next week and I needhelp
0
6 years ago
#17
(Original post by kritz20)
Can you explain the 11th question and the 20thquestion in edexcel physics june 2014 (IAL) unit 2 paper. I do not understandthe answer given in the marking scheme. I have mock exams next week and I needhelp
11:
Light is a transverse wave, and as such can be polarised. Laserlight is already polarised. This means that the wave is 'cut' into only one direction of motion. Think of it as it passing through a cheese grater, or squeezing through a gap. There is a good diagram here
Spoiler:
Show
20: Basically, the waves that come out of the interferometer are of a different path difference so therefore the peaks and troughs are 'misaligned' so to speak. This means the waves superimpose on each other, ie they cancel in places where they are both opposite signs etc.

They come out as a single wave where they have path difference of where is an integer. (whole number)
Basically, they come out as a single wave when they are exactly an integer wavelength apart.

They cancel when where is an integer. This basically means when they are wavelengths apart they cancel.
Spoiler:
Show
You need to revise these topics it seems :P
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#18
(Original post by The-Spartan)
11:
Light is a transverse wave, and as such can be polarised. Laserlight is already polarised. This means that the wave is 'cut' into only one direction of motion. Think of it as it passing through a cheese grater, or squeezing through a gap. There is a good diagram here
Spoiler:
Show
20: Basically, the waves that come out of the interferometer are of a different path difference so therefore the peaks and troughs are 'misaligned' so to speak. This means the waves superimpose on each other, ie they cancel in places where they are both opposite signs etc.

They come out as a single wave where they have path difference of where is an integer. (whole number)
Basically, they come out as a single wave when they are exactly an integer wavelength apart.

They cancel when where is an integer. This basically means when they are wavelengths apart they cancel.
Spoiler:
Show
You need to revise these topics it seems :P
Thank you so much.... Can you also explain why the resistance of a negative temperature coefficient thermistor decreases when the potential difference is increased with relation the equation I= nAvq
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