# Photoelectric effect

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A metal gives out photoelectrons that have a stopping voltage of2.6v

Will the light of a wavelength of 615 nm cause photoelectrons to be ejected?

Will the light of a wavelength of 615 nm cause photoelectrons to be ejected?

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#2

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(Original post by

TSR Physics forum does not provide "do my homework" service, so there are some guidelines that we expect everyone who is posting questions/problems to follow.

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**Hallouminatus**)TSR Physics forum does not provide "do my homework" service, so there are some guidelines that we expect everyone who is posting questions/problems to follow.

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Will the light of a wavelength of 615 nm cause photoelectrons to be ejected?

2) I worked out the work function but am not sure what to do with it and it is negative which I'm not sure how to deal with

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#4

(Original post by

1) A metal gives out photoelectrons that have a stopping voltage of2.6v

Will the light of a wavelength of 615 nm cause photoelectrons to be ejected?

2) I worked out the work function but am not sure what to do with it and it is negative which I'm not sure how to deal with

**stdevlin03**)1) A metal gives out photoelectrons that have a stopping voltage of2.6v

Will the light of a wavelength of 615 nm cause photoelectrons to be ejected?

2) I worked out the work function but am not sure what to do with it and it is negative which I'm not sure how to deal with

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(Original post by

The graph on this page may help explain why work function is negative, and what to do with it. http://physicsnet.co.uk/a-level-phys...ectric-effect/

**Hallouminatus**)The graph on this page may help explain why work function is negative, and what to do with it. http://physicsnet.co.uk/a-level-phys...ectric-effect/

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#6

Work function is always negative. Energy of photon + work function of metal = energy of emitted photoelectron. If the sum is negative, no electron can be emitted.

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(Original post by

Work function is always negative. Energy of photon + work function of metal = energy of emitted photoelectron. If the sum is negative, no electron can be emitted.

**Hallouminatus**)Work function is always negative. Energy of photon + work function of metal = energy of emitted photoelectron. If the sum is negative, no electron can be emitted.

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(Original post by

Work function is always negative. Energy of photon + work function of metal = enesrgy of emitted photoelectron. If the sum is negative, no electron can be emitted.

**Hallouminatus**)Work function is always negative. Energy of photon + work function of metal = enesrgy of emitted photoelectron. If the sum is negative, no electron can be emitted.

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#9

(Original post by

so for this question how would that apply

**stdevlin03**)so for this question how would that apply

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(Original post by

tbh, I'm a bit confused by this myself. Is there any other info or context?

**Hallouminatus**)tbh, I'm a bit confused by this myself. Is there any other info or context?

that is the exact question

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#11

(Original post by

A metal gives out photoelectrons that have stopping voltage of 2.6 v will light of wavelength cause photoelectrons to be ejected?

that is the exact question

**stdevlin03**)A metal gives out photoelectrons that have stopping voltage of 2.6 v will light of wavelength cause photoelectrons to be ejected?

that is the exact question

From the wavelength, you can work out the energy of the incident light.

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(Original post by

From the stopping potential, you can work out the kinetic energy of the electrons.

From the wavelength, you can work out the energy of the incident light.

**Sinnoh**)From the stopping potential, you can work out the kinetic energy of the electrons.

From the wavelength, you can work out the energy of the incident light.

and f = 3*10^8/ 615*10^-9

how do I answer the question from here?

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#13

(Original post by

so the Ek is 2.6x1.6*10^-19

and f = 3*10^8/ 615*10^-9

how do I answer the question from here?

**stdevlin03**)so the Ek is 2.6x1.6*10^-19

and f = 3*10^8/ 615*10^-9

how do I answer the question from here?

Does it mention the work function of the metal anywhere?

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#14

**Sinnoh**)

From the stopping potential, you can work out the kinetic energy of the electrons.

From the wavelength, you can work out the energy of the incident light.

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#15

(Original post by

OK, I might be missing something really obvious here, or misreading the question, but it still looks like something is missing. To answer the question whether the 615 mm light will cause emission of a photoelectron, we need to know the work function, but the information that electrons are emitted at 2.6 eV is not sufficient to give the work function unless we know the frequency of the incident light.

**Hallouminatus**)OK, I might be missing something really obvious here, or misreading the question, but it still looks like something is missing. To answer the question whether the 615 mm light will cause emission of a photoelectron, we need to know the work function, but the information that electrons are emitted at 2.6 eV is not sufficient to give the work function unless we know the frequency of the incident light.

Although if the energy of the photons is less than the energy of the photoelectrons, then it can be answered because the answer is "definitely not".

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co

Could you find the frequency using the wavelength and the threshold frequency and if it's lower it will not emit photoelectrons??

(Original post by

Yeah it's a bit meaningless without the work function.

Although if the energy of the photons is less than the energy of the photoelectrons, then it can be answered because the answer is "definitely not".

**Sinnoh**)Yeah it's a bit meaningless without the work function.

Although if the energy of the photons is less than the energy of the photoelectrons, then it can be answered because the answer is "definitely not".

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#17

(Original post by

co

Could you find the frequency using the wavelength and the threshold frequency and if it's lower it will not emit photoelectrons??

**stdevlin03**)co

Could you find the frequency using the wavelength and the threshold frequency and if it's lower it will not emit photoelectrons??

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(Original post by

All you need to do is compare the photon energy for a 615nm photon to the electron kinetic energy + work function

**Sinnoh**)All you need to do is compare the photon energy for a 615nm photon to the electron kinetic energy + work function

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(Original post by

Well you could just work out the photon energy directly as . Is it higher or lower than the kinetic energy of the photoelectrons?

Does it mention the work function of the metal anywhere?

**Sinnoh**)Well you could just work out the photon energy directly as . Is it higher or lower than the kinetic energy of the photoelectrons?

Does it mention the work function of the metal anywhere?

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#20

(Original post by

can I find the work function using hf - phi = Ekmax

**stdevlin03**)can I find the work function using hf - phi = Ekmax

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