Doppler effect

  • #1

Homework Statement



can anyone explain why reletive velocity is (v-u), based on my understanding, as the obesrvers moving away, the distance of the f th wavefront and first waavefront increases. so i would say it's v+u . correct me if i'm wrong. thanks.

Homework Equations





The Attempt at a Solution

 

Attachments

  • IMG_20140606_104502[1].jpg
    IMG_20140606_104502[1].jpg
    33.4 KB · Views: 413

Answers and Replies

  • #2
906
88
The distance between wave fronts appears to increase, yes, but that is because the relative speed is also decreasing as the observer accelerates away. If u=v then the wave would never reach you.
 
  • #3
1,948
201
The wave and the observer are moving in the same direction. Their relative speed is v-u. If they were moving in the opposite direction than the relative speed would be v+u.
 
Last edited:
  • #4
CWatters
Science Advisor
Homework Helper
Gold Member
10,541
2,314
If two cars travel on the freeway at similar speeds in the same direction the relative velocity between them is small. It's not going to be the sum of their speeds.
 

Related Threads on Doppler effect

  • Last Post
Replies
1
Views
885
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
0
Views
1K
  • Last Post
Replies
6
Views
3K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
1
Views
961
  • Last Post
Replies
6
Views
939
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
24
Views
2K
Top