Previous in Forum: Interfacing DDR LVDS Outputs to uC   Next in Forum: Medium Voltage Variable Speed Drive Harmonics
Close
Close
Close
20 comments
Rate Comments: Nested
Power-User
Hobbies - Musician - New Member

Join Date: Dec 2014
Posts: 418
Good Answers: 3

Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 7:16 AM

Hi guys, im not quite good on the above. I'll appreciate you could do some starters scratch note to work to. How can we relate wavelength to projected area.

__________________
"When I thought I exceeded to be wise but wisdom was far from me" -King Solomon
Register to Reply
Pathfinder Tags: photoelectric effect
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#1

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 7:40 AM

Whatever are you talking about?

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Power-User
Hobbies - Musician - New Member

Join Date: Dec 2014
Posts: 418
Good Answers: 3
#8
In reply to #1

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:55 AM

Hi John, yes. Ive been to some whatever these days. Hehe hope your well.

__________________
"When I thought I exceeded to be wise but wisdom was far from me" -King Solomon
Register to Reply
Guru

Join Date: Mar 2012
Location: Out of your mind! Not in sight!
Posts: 4424
Good Answers: 108
#2

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 7:46 AM

Photoelectric?

Wave length?

Area?

Maybe describe what you are trying to do.

So far light does not get around corners. So the area of "projection" is the same area that you project the light at.

This should be your starting point until you can come up with something else.

__________________
Common Sense Dictates
Register to Reply
Guru
Engineering Fields - Optical Engineering - Member Engineering Fields - Engineering Physics - Member Engineering Fields - Systems Engineering - Member

Join Date: Apr 2010
Location: Trantor
Posts: 5363
Good Answers: 647
#3

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:38 AM

It's a simple equation:

Wavelength = K • ( Projected Area ), where K is in nanometers per steradian.

Except, there is no such constant as K.

Because there is no actual relationship between wavelength and projected area.

__________________
Whiskey, women -- and astrophysics. Because sometimes a problem can't be solved with just whiskey and women.
Register to Reply
Power-User
Hobbies - Musician - New Member

Join Date: Dec 2014
Posts: 418
Good Answers: 3
#6
In reply to #3

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:51 AM

I mean like if you want to design an antenna for FM radio frequencies how would you size it? Is it small or big one? How should it be size? Compare to am radio? High frequency, shorter wave length needs long or big antennas? Or low frequencies long wave length needs just small antenna? What you think?

__________________
"When I thought I exceeded to be wise but wisdom was far from me" -King Solomon
Register to Reply
Guru

Join Date: Mar 2012
Location: Out of your mind! Not in sight!
Posts: 4424
Good Answers: 108
#9
In reply to #6

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:59 AM

You might want to look into optics a bit deeper.

Your initial question is not what you ask here.

So what exactly is the application?

__________________
Common Sense Dictates
Register to Reply
Guru

Join Date: Nov 2007
Location: Eastern Arizona mountains on Route 666 about a mile from God's country
Posts: 1676
Good Answers: 122
#4

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:39 AM

Is this for photometric analysis?

__________________
They said; "Brain size?" I heard; "Train size?" so I said: "I'll take a small one, thank you."
Register to Reply
Guru

Join Date: Apr 2010
Location: About 4000 miles from the center of the earth (+/-100 mi)
Posts: 9910
Good Answers: 1141
#5

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:45 AM

The energy of a photon is inversely proportional to the wavelength. It takes a certain amount of energy, the work function, to remove an electron from a metal surface so a photon has to have a short enough wavelength to exceed this energy. (The work function depends on the metal.) The intensity of the light (number of photons per unit time) with wavelength shorter than the critical wavelength determines the number of electrons (current) that will be removed from the metal.

So if you have a certain intensity light shorter than the critical wavelength (photons per area per unit time) then the amount of photocurrent would be proportional to the area.

https://en.wikipedia.org/wiki/Photoelectric_effect

Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#7
In reply to #5

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:53 AM

Or to put it another way, "if the wavelength's too long, the area is irrelevant".

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Power-User
Hobbies - Musician - New Member

Join Date: Dec 2014
Posts: 418
Good Answers: 3
#10
In reply to #7

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:00 AM

Like spectrum 400 to 900 nm wavelengths, how would i approach the smallest receptor/absorber for it? Id like to do the math, but i ain got the right foundation yet. I really hope someone could help, if he she be kind. Thanks in advance.

__________________
"When I thought I exceeded to be wise but wisdom was far from me" -King Solomon
Register to Reply
Guru

Join Date: Apr 2010
Location: About 4000 miles from the center of the earth (+/-100 mi)
Posts: 9910
Good Answers: 1141
#18
In reply to #10

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 4:32 PM

First, you have to have the right kind of metal. Look on the left side of the periodic table. The alkalai metals don't hold on to their electrons to tightly.

900 nm = 1.37760 ev

400 nm = 3.09961 ev

http://www.calctool.org/CALC/other/converters/e_of_photon

Here is a table of work functions for common metals:

http://www.knowledgedoor.com/2/elements_handbook/photoelectric_work_function.html

The energy of the electrons coming off is the photon energy minus the work function for the chosen metal.

The shorter the wavelength the greater the voltage (electron energy in ev)

The brighter the light, the more the current (number of electrons).

The amount of light energy per unit time would be the product of the area and the light intensity: Energy = area x (Energy/area) and would be roughly equal to (electron energy + work function) x current

Register to Reply
Guru

Join Date: Mar 2012
Location: Out of your mind! Not in sight!
Posts: 4424
Good Answers: 108
#11
In reply to #7

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:00 AM

Or you just need a bigger antenna!

__________________
Common Sense Dictates
Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#13
In reply to #11

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:27 AM

Thought we were talking about the photoelectric effect. But who reads thread titles, anyway?

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Power-User
Hobbies - Musician - New Member

Join Date: Dec 2014
Posts: 418
Good Answers: 3
#15
In reply to #13

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:51 AM

A o yes, smart ideas should be keep close in discretion, thanks John.

__________________
"When I thought I exceeded to be wise but wisdom was far from me" -King Solomon
Register to Reply
Guru
Engineering Fields - Optical Engineering - Member Engineering Fields - Engineering Physics - Member Engineering Fields - Systems Engineering - Member

Join Date: Apr 2010
Location: Trantor
Posts: 5363
Good Answers: 647
#19
In reply to #13

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 8:06 PM

Yeah....

__________________
Whiskey, women -- and astrophysics. Because sometimes a problem can't be solved with just whiskey and women.
Register to Reply
Guru

Join Date: Mar 2012
Location: Out of your mind! Not in sight!
Posts: 4424
Good Answers: 108
#20
In reply to #13

Re: Photoelectric Effect, Wave Length To Area Relationship

07/08/2015 3:19 AM

Are we?

I read along in the thread. From OP at #6

I mean like if you want to design an antenna for FM radio frequencies how would you size it? Is it small or big one?

__________________
Common Sense Dictates
Register to Reply
Power-User
Hobbies - Musician - New Member

Join Date: Dec 2014
Posts: 418
Good Answers: 3
#12
In reply to #5

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:04 AM

Thanks Rix, youre such a someone to rely on.

__________________
"When I thought I exceeded to be wise but wisdom was far from me" -King Solomon
Register to Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15600
Good Answers: 981
#14

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:47 AM

As Rixter and another pointed out the photoelectric effect is a different phenomena from radio frequency reception. The area of the sensor, photo cell, etc. will not be a critical factor with sub-micron wave lengths of light.

What you seem to interested in is called solid state theory. The link is to the Rössler introduction textbook at Springer. Don't let the "introduction" title fool you. This textbook is for a post graduate class. Digesting this one textbook would likely take the complete semester.

Springer has been releasing many of their older textbooks as completely free to download. I'm not sure if that link will work for everyone.

__________________
"Don't disturb my circles." translation of Archimedes last words
Register to Reply
Power-User
Hobbies - Musician - New Member

Join Date: Dec 2014
Posts: 418
Good Answers: 3
#17
In reply to #14

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:52 AM

Hi redfred. Yeah, this is good. Thank you.

__________________
"When I thought I exceeded to be wise but wisdom was far from me" -King Solomon
Register to Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#16

Re: Photoelectric Effect, Wave Length To Area Relationship

07/07/2015 9:51 AM

Get yourself a copy of the Amateur Radio Relay League (ARRL) Handbook, it has all the information/formulas you want/need and it's written so that non-math/non-engineering type people can understand it, if they make the effort.

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Register to Reply
Register to Reply 20 comments
Copy to Clipboard

Users who posted comments:

IdeaSmith (4); JohnDG (3); Kulas (6); RAMConsult (1); redfred (1); Rixter (2); SHOCKHISCAN (1); Usbport (2)

Previous in Forum: Interfacing DDR LVDS Outputs to uC   Next in Forum: Medium Voltage Variable Speed Drive Harmonics

Advertisement