Solving for Magnitude of Sirius (-1.5) Through Triple Window

[Jussi Lundahl]

Homework Statement

Stars are observed through a triple window.
Each surface reflects away 15% of the incident light.
a) What is the magnitude of Sirius (m = -1.5) seen
through the window?

And I know that the solution is -0,97.

Homework Equations

m₁-m₂=-2,5*log₁₀*(F₁/F₂)

The Attempt at a Solution

I have no idea what to do...

 

[Bandersnatch]

Ok, start by telling us what are the F1 and F2 in the equation.

 

[Voltageisntreal]

If 15% is deflected each time, then sirius's intensity, which let's say is 1 becomes 0.614 since (0.85)^3=0.614

Then, log(1/0.614)*2.5=0.5295

0.5295 is hence the difference between the apparnt magnitudes of the star after it has passed through the three windows. -1.5+0.5295=-0.9704

There's the answer.

 

[Jussi Lundahl]

Ok, start by telling us what are the F1 and F2 in the equation.

I think those are called flux density in English. $$F=\frac{L}{4 \pi r^2}$$, where the L is luminosity and r is radius. $$ L= \omega r^2$$ where $$\omega$$ is solid angle?? and r is radius.

 

[Jussi Lundahl]

If 15% is deflected each time, then sirius's intensity, which let's say is 1 becomes 0.614 since (0.85)^3=0.614

Then, log(1/0.614)*2.5=0.5295

0.5295 is hence the difference between the apparnt magnitudes of the star after it has passed through the three windows. -1.5+0.5295=0.9704

There's the answer.

Thank you! You saved my day :)

 

[Bandersnatch]

There's the answer.

Please, do not provide full answers to questions posted in the homework forum. Spoon-feeding is against the rules.

 

[Voltageisntreal]

Please, do not provide full answers to questions posted in the homework forum. Spoon-feeding is against the rules.

;o, mb didn't kno rip

 

[gneill]

;o, mb didn't kno rip

Text speak is also not permitted!