Photoelectric exp - calculate intensity of incident light

Click For Summary

Homework Help Overview

The discussion revolves around a photoelectric effect experiment where the original poster attempts to calculate the intensity of incident light based on the photoelectric current generated. The context involves understanding the relationship between current, the number of ejected electrons, and incident photons.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants question the relationship between photoelectric current and the number of electrons ejected, as well as the connection to incident photons. There are discussions about the units of the calculated intensity and the validity of the original poster's calculations.

Discussion Status

The discussion is ongoing, with participants providing guidance on checking units and questioning the correctness of the original calculations. Multiple interpretations of the problem are being explored, particularly regarding the relationships involved in the photoelectric effect.

Contextual Notes

There appears to be confusion regarding the units of the calculated intensity, and participants are addressing potential misunderstandings in the original poster's approach to the problem.

desmond iking
Messages
284
Reaction score
2

Homework Statement


In an photoelectric effect experiment , a photoelectric current of 100µA is obtained when lights of 550nm is incident on metal cathode of surface area 1.0cm^2 ... calculate the intensity of the incident light. The ans is 2.26w/m^2

Homework Equations

The Attempt at a Solution



intensity= power /area
intensity= (voltage x current) /area
intensity= ( (hc/λ) x I ) / area
= (6.63x10^-34)(3x10^8)(100x10^-6) / (550x10^-9)(1.0x10^-4) = 3.61x10^-19 (W/m^2 )

why am i wrong?
[/B]
 
Physics news on Phys.org
How is the photoelectric current related to the number of electrons ejected? What is the relation between the number of electrons ejected and the number of the incident photons?
If you check the unit of your result, it is not W/m2.
 
  • Like
Likes   Reactions: desmond iking
ehild said:
How is the photoelectric current related to the number of electrons ejected? What is the relation between the number of electrons ejected and the number of the incident photons?
If you check the unit of your result, it is not W/m2.

can you please tell me what's the unit of my 3.61x10^-19 should be? i am confused now.
 
The problem is not with the units. If you check the unit of your result and it is not what it should be then your solution is wrong. Your solution is wrong, as its dimension is not energy/(time area).
Read the first two sentences of my previous post.

ehild
 

Similar threads

Replies
4
Views
2K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 10 ·
Replies
10
Views
3K
Replies
6
Views
13K
Replies
3
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
Replies
3
Views
2K
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 3 ·
Replies
3
Views
6K