## Optics B/C

cngu23
Member
Posts: 248
Joined: March 12th, 2011, 4:57 pm
Division: C
State: MD
Location: Maryland
Has thanked: 0
Been thanked: 1 time

### Re: Optics B/C

JSGandora wrote:If it's moving away, then the wavelength will increase therefore it's a red shift. If it's moving closer, then the wavelength will decrease meaning it will be a blue shift.
For calculation, what is the unit measure of z in the redshift formula?
Marriotts Ridge 11-
Walter Johnson 09-11

13 MD Regional/State
Material S (2/-) TPS (-/2)
12 MD Regional/State
Remote S(2/6) Water Q(2/4) Optics (-/5)
11 MD Regional
Remote S(2) Eco(2) D Planet(3)

AlphaTauri
Staff Emeritus
Posts: 829
Joined: September 11th, 2009, 1:41 pm
State: PA
Location: 04h 35m 55.239s, +16° 30′ 33.49″
Has thanked: 0
Been thanked: 0
Contact:

### Re: Optics B/C

cngu23 wrote:
JSGandora wrote:If it's moving away, then the wavelength will increase therefore it's a red shift. If it's moving closer, then the wavelength will decrease meaning it will be a blue shift.
For calculation, what is the unit measure of z in the redshift formula?
z has no unit - it's just a dimensionless number.
Hershey Science Olympiad 2009 - 2014
Volunteer for Michigan SO 2015 - 2018

]\/[ Go Blue!

JSGandora
Member
Posts: 613
Joined: December 25th, 2010, 12:09 pm
Division: C
State: NJ
Has thanked: 0
Been thanked: 0

### Re: Optics B/C

Instead of using that, which doesn't help at all in this case, use the Relativistic Doppler Shift equation which is this:
http://hyperphysics.phy-astr.gsu.edu/hb ... ldop2.html

cngu23
Member
Posts: 248
Joined: March 12th, 2011, 4:57 pm
Division: C
State: MD
Location: Maryland
Has thanked: 0
Been thanked: 1 time

### Re: Optics B/C

JSGandora wrote:Instead of using that, which doesn't help at all in this case, use the Relativistic Doppler Shift equation which is this:
http://hyperphysics.phy-astr.gsu.edu/hb ... ldop2.html
So if I use this equation instead of the one of doppler effect, for my previous problem, what would I use for v?

And there may be an error in the answer key for my previous problem. If an object is traveling away from the observer, I believe that the observed frequency would be less than the actually frequency, but the answer says that it increases by a factor of 10.
Can someone verify this?

Camas Division B test in test exchange.
Marriotts Ridge 11-
Walter Johnson 09-11

13 MD Regional/State
Material S (2/-) TPS (-/2)
12 MD Regional/State
Remote S(2/6) Water Q(2/4) Optics (-/5)
11 MD Regional
Remote S(2) Eco(2) D Planet(3)

JSGandora
Member
Posts: 613
Joined: December 25th, 2010, 12:09 pm
Division: C
State: NJ
Has thanked: 0
Been thanked: 0

### Re: Optics B/C

Yes, the frequency should decrease. I think I took that test before and my answer disagreed with the answer key.

Infinity Flat
Member
Posts: 274
Joined: March 12th, 2010, 4:00 pm
State: WA
Location: Camas, WA
Has thanked: 0
Been thanked: 0

### Re: Optics B/C

JSGandora wrote:Yes, the frequency should decrease. I think I took that test before and my answer disagreed with the answer key.
My mistake, I used the Doppler Effect calculator linked above, and I may or may not have solved in the wrong direction.
(State, Nationals)
2013: Astro (2, 6) / Chem (2, 5) / Circuits (8, 36) / Diseases (1,1) / Fermi (N/A, 24) / Materials (1, N/A)
2012 : Astro (1, 11) / Chem (N/A, 13) / Diseases (3, 1) / Optics (2, 3) / Sounds (2, 1)
2011: Astro(2,11) / Diseases (1,27) / Optics (1,13) / Proteins (2,15)

cngu23
Member
Posts: 248
Joined: March 12th, 2011, 4:57 pm
Division: C
State: MD
Location: Maryland
Has thanked: 0
Been thanked: 1 time

### Re: Optics B/C

JSGandora wrote:Yes, the frequency should decrease. I think I took that test before and my answer disagreed with the answer key.
Alright. So should the correct answer be 2.56 x 10^6? I used the doppler effect equation.
Marriotts Ridge 11-
Walter Johnson 09-11

13 MD Regional/State
Material S (2/-) TPS (-/2)
12 MD Regional/State
Remote S(2/6) Water Q(2/4) Optics (-/5)
11 MD Regional
Remote S(2) Eco(2) D Planet(3)

Infinity Flat
Member
Posts: 274
Joined: March 12th, 2010, 4:00 pm
State: WA
Location: Camas, WA
Has thanked: 0
Been thanked: 0

### Re: Optics B/C

cngu23 wrote:
JSGandora wrote:Yes, the frequency should decrease. I think I took that test before and my answer disagreed with the answer key.
Alright. So should the correct answer be 2.56 x 10^6? I used the doppler effect equation.
Using this calculator for relativistic Doppler effect, I get 8.00 * 10^5 Hz.
(State, Nationals)
2013: Astro (2, 6) / Chem (2, 5) / Circuits (8, 36) / Diseases (1,1) / Fermi (N/A, 24) / Materials (1, N/A)
2012 : Astro (1, 11) / Chem (N/A, 13) / Diseases (3, 1) / Optics (2, 3) / Sounds (2, 1)
2011: Astro(2,11) / Diseases (1,27) / Optics (1,13) / Proteins (2,15)

JSGandora
Member
Posts: 613
Joined: December 25th, 2010, 12:09 pm
Division: C
State: NJ
Has thanked: 0
Been thanked: 0

### Re: Optics B/C

Sooo confusing @.@

So plugging the numbers in and using Wolfram Alpha, I get 1.25*10^6:

http://www.wolframalpha.com/input/?i=5s ... %29*10%5E6

cngu23
Member
Posts: 248
Joined: March 12th, 2011, 4:57 pm
Division: C
State: MD
Location: Maryland
Has thanked: 0
Been thanked: 1 time

### Re: Optics B/C

JSGandora wrote:Sooo confusing @.@

So plugging the numbers in and using Wolfram Alpha, I get 1.25*10^6:

http://www.wolframalpha.com/input/?i=5s ... %29*10%5E6
My bad. I was using the wrong doppler effect equation. The one for sound.

for your wolframalpha calculation, you used 2.6461 instead of 2.8481. And also, v should be the velocity of the wave, not frequency. But since they are directly related, should that not matter?

EDIT: Actually, I used a calculator to verify your wolfram alpha calculation with 2.8481 instead of 2.6461. It turned out to be 8 x 10^5
Last edited by cngu23 on February 28th, 2012, 7:40 pm, edited 2 times in total.
Marriotts Ridge 11-
Walter Johnson 09-11

13 MD Regional/State
Material S (2/-) TPS (-/2)
12 MD Regional/State
Remote S(2/6) Water Q(2/4) Optics (-/5)
11 MD Regional
Remote S(2) Eco(2) D Planet(3)

### Who is online

Users browsing this forum: No registered users and 1 guest