# How Do You Calculate the Width of a Gap Affecting Radio Reception?

• kittycat
In summary, the conversation revolves around a person seeking help with physics problems, specifically regarding radio reception and a Michelson-Morley interferometer. They are struggling with calculating distances and angles to find the width between two buildings and the index of refraction for a gas, and also have difficulty drawing a diagram for another problem. They express a sense of urgency and impatience for help.
kittycat

Question1: You are driving down the road in your car and you notice that your favorite radio station that you are listening to, 95.7 MHz, is going in and out. You look out and over and you see two long buildings with a gap in them. You know that you are a distance of 100 meters from the buildings. As you pass directly across from the gap in the buildings, you notice that the readio reception is the strongest. From there it continually get worse and worse until you have traveled 17.6 meters where there is no reception. It then comes back in but goes out agian after traveling 37.1 meters from the center point (19.5 m further down the road), and it goes out agian at 61.1 meters from where you started measuring.
What is the width of the gap between the buildings?

**okay, so I know that D*sin theta = m*lmabda, fequency is also 95.7 MHz and lamda=c/f. It's just like Single Slit Diffraction. So I calculated all the angles theta in order to find D, but now I've got a bunch of angles and many Ds, am I heading the right direction?? it seems all complicated and worng, can someone please tell me how can i get the D (distance between the buildings) that I want?

Question 2:
This is a Michelson-Morley Interferometer (Diagram not part of the question):

Question: A glass container is placed along arm 2 (the arm right above L_A in the diagram) of the interferometer. The glass container is 1 cm long (you may ignore the thickness of the glass).
At first, the container is empty and the mirror along the horizontal line (the mirror that is placed vertically) is adjusted so that a bright fringe is observed at the detector. Now, a gas of unknown index of reflection is slowly allowed to enter to container. During the time this occurs, 1624 changes between bright and dark are observed to occur while it is filling up. The source is known to have a wavelength of 550 nm. What is the index of refraction for this gas?

**I know that The speed of light in a medium of refractive index n is given by v = c/n where c is the speed of light in a vacuum. but I don't know to solve the whole thing.

Question 3: I've attached the picture and the quesiton, I've tried drawing it, but it looks too wrong, but i have no idea how to make it look right.

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• CCF08302008_00000.jpg
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You need to be patient: it's Saturday!

cristo said:
You need to be patient: it's Saturday!

:) sorry! It's like really really urgent, that's why I'm asking.

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