Electromagnetic wave striking a small pocket mirror

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Homework Help Overview

The discussion revolves around a problem involving a plane electromagnetic wave striking a small pocket mirror, focusing on the momentum transfer and force exerted by the wave on the mirror. The subject area includes concepts from electromagnetism and wave mechanics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to calculate the momentum transferred to the mirror using the intensity of the wave and its relationship to energy. They express difficulty in determining the energy density needed for this calculation. Other participants question the relationship between energy flux and momentum flux, seeking clarification on how these concepts interrelate for electromagnetic waves.

Discussion Status

Participants are exploring various aspects of the problem, with some providing insights into the relationships between energy and momentum in electromagnetic waves. There is an ongoing exchange of ideas, but no explicit consensus has been reached regarding the calculations or concepts involved.

Contextual Notes

The original poster mentions specific values and equations related to the problem, indicating a structured approach to solving the questions posed. However, there are indications of confusion regarding the application of these concepts, particularly in the context of the homework constraints.

Minihoudini
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Homework Statement


a plane electromagnetic wave of intensity 6.00 W/m^2, moving in the x direction, strikes a small pocket mirror of area 40.0cm^2, held in the yz plane.
(a) what momentum does the wave transfer to the mirror each second?
(b) find the force that the wave exerted on the mirror?
(c) explain the relationship between a and b


Homework Equations


I know how to get (b) and (c) but the first one is giving me the most trouble. I need help find U in order to get momentum from p= U/c


The Attempt at a Solution



given S I tried to calculate E and B to find Ue and Ub. I used I= E^2/2(mu)c arranged to be E= Sqrt and i used a few others to try to find U but nothing has been working. its telling me that the answer is 1.60 x 10^-10. I am getting answers close to the answer but not the answer.
 
Physics news on Phys.org
How does energy flux (S) relate to momentum flux?
 
I meant I
 
Minihoudini said:
I meant I
Same thing. How does energy relate to momentum for an EM wave?
 

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