YouTube Lecture # 26

1. 1
A physics professor claims in court that the reason he
went through the red light (λ = 650 nm) was that, due to
his motion, the red color was Doppler shifted to green (λ
= 550 nm). How fast was he going?

2. 2
Helping Tools
No.1

3. 3

4. 4
No.2
Solution

5. 5
0
0 0
Doppler Effect
1
1
u
c u f c u f c
f f
u
c u f c u f
c
+
+ +
=  =  =
− − −

6. 6
2
2 2
0
2 2
2
0
( ) 1 1
(650 )
(550 )
( ) 1 1
c u u
nm c u
c c
c u u nm c u
c c




+ +
+
 =  =  =
−
− −

7. 7
422500
1.3967
302500
1.3967(300000000 ) 300000000
c u c u
c u c u
m m
u u
s s
+ +
 =  =
− −
 − = +

8. 8
419010000 1.3967 300000000
(419010000 300000000) (1 1.3967)
m m
u u
s s
m
u
s
 − = +
 − = +

9. 9
7
119010000 2.3967
49655776.69 5 10
m
u
s
m m
u X
s s
 =
 = 