Determine Radiation pressure given the fraction of total absorption

  • Thread starter MrMoose
  • Start date
  • #1
23
0

Homework Statement



Radiation of intensity I is normally incident on an object that absorbs a fraction frac of it and reflects the rest back along the original path. What is the radiation pressure on the object?

Homework Equations



Radiation pressure Pr (force/unit area)

Pra = I/c (total absorption)

Prr = 2I/c (total reflection back along path)

The Attempt at a Solution



The object absorbs a fraction frac of the intensity, which I translate mathematically as:

Pra = (frac)*I / c

This would mean that the total intensity reflected is:

Prr = 2*(1 - frac)*I/c

Unfortunately the answer is: Pra = (2 - frac)*I / c

I don't know how they came to this conclusion. Thanks in advance, MrMoose
 

Answers and Replies

  • #2
6,054
391
So how do you go from Pra and Prr to total pressure?
 
  • #3
23
0
Holy smokes. Thanks.

Pra + Prr = (frac)*I/c + 2*(1-frac)*I/c = I*frac/c + 2*I/c - 2*frac*I/c

= (2 - frac)*I / c
 

Related Threads on Determine Radiation pressure given the fraction of total absorption

Replies
1
Views
515
  • Last Post
Replies
0
Views
4K
  • Last Post
Replies
13
Views
4K
  • Last Post
Replies
3
Views
8K
Replies
3
Views
1K
Replies
2
Views
4K
Replies
2
Views
3K
Replies
1
Views
3K
  • Last Post
Replies
2
Views
2K
Top