Sun Interference astronomy question

In summary: Ok, so that is the problem right now i have a diagram and understand destructive interference will occur when (n - 1/2 )λWavelength in this situation is V = Fλtherefore λ = 60x10^6 / cλ = 5mthe attachment is of my current diagram ( sorry for the crude drawings, only had paint avalible).Cheers!In summary, Vanesch explains that if an antenna is located on the coastline 25m above the sea level and the radio waves have a frequency of 60 MHZ, destructive interference will occur at a minimum angle above the horizon for the sun.
  • #1
lektor
56
0
A radio wave undergoes a phase shift of 180 degrees when it reflects from the calm surface of the ocean. In early days of radioastronomy, Australian Astronomers observed the interference between a radio wave arriving at the their antena on a direct path from the sun and on a path involving one reflecting on the sea surface. If their antenna was located on the coastline 25m above the sea level and the radio waves had a frequency of 60 MHZ, find the least angle above the horizon for the sun that results in destructive interference of the waves at the receivng antenna.

The identity cos 2θ = 1-2sin^2θ


Ok, so that is the problem right now i have a diagram and understand destructive interference will occur when (n - 1/2 )λ

Wavelength in this situation is

V = Fλ
therefore λ = 60x10^6 / c
λ = 5m

the attachment is of my current diagram ( sorry for the crude drawings, only had paint avalible).

Cheers.
 

Attachments

  • diagram.JPG
    diagram.JPG
    7.6 KB · Views: 448
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  • #2
lektor said:
A radio wave undergoes a phase shift of 180 degrees when it reflects from the calm surface of the ocean. In early days of radioastronomy, Australian Astronomers observed the interference between a radio wave arriving at the their antena on a direct path from the sun and on a path involving one reflecting on the sea surface. If their antenna was located on the coastline 25m above the sea level and the radio waves had a frequency of 60 MHZ, find the least angle above the horizon for the sun that results in destructive interference of the waves at the receivng antenna.
The identity cos 2θ = 1-2sin^2θ
Ok, so that is the problem right now i have a diagram and understand destructive interference will occur when (n - 1/2 )λ
Wavelength in this situation is
V = Fλ
therefore λ = 60x10^6 / c
λ = 5m
the attachment is of my current diagram ( sorry for the crude drawings, only had paint avalible).
Cheers.
Some hints: your drawing is misleading: you should consider rays coming from the sun *parallel*, and you should calculate, from a common wavefront onwards (perpendicular to the incoming rays from the sun), what is the total path a) directly, and b) through reflection, and translate that in a number of wavelengths. You should then add half a wavelength to the reflected path (the 180 degree phase flip) and compare.
 
  • #3
Hi vanesch,

I revised my diagram as to how you asked and attempted to redo the question with unfortunately no avail.

These questions to do with reflection interference have been plagueing me for most of this year and if it is not too much would you possibly be able to do the question and show each step of working.. possibly with notes on the working.

Cheers if this is possible :)
 
  • #4
Hi,
I attached a diagram that should be more suggestive. Sorry, I have drawn it quite quickly...
The idea is to calculate the path of beam 1 and of beam 2 up to R, the position of the receiver, starting from a (perpendicular) wavefront: points x and y.
In fact, you can even move the wavefront (points x and y) to the point of reflexion on the sea surface...
 

Attachments

  • pbreflexion.GIF
    pbreflexion.GIF
    1.8 KB · Views: 511

What is Sun Interference in astronomy?

Sun interference in astronomy refers to the phenomenon when the Sun's light and radio waves interfere with observations of astronomical objects. This interference can affect the quality and accuracy of data collected by telescopes and other instruments.

How does Sun Interference impact astronomical observations?

Sun interference can affect astronomical observations in several ways. It can cause a decrease in image contrast, making it difficult to see faint objects. It can also introduce stray light, which can mask or distort the data being collected. In extreme cases, Sun interference can completely overwhelm the signals from astronomical objects, making them impossible to observe.

When does Sun Interference occur?

Sun interference occurs when the Sun is in the same general direction as the astronomical object being observed. This can happen during sunrise and sunset, as well as other times during the day depending on the location and orientation of the telescope or instrument.

How do scientists minimize the effects of Sun Interference?

Scientists use a variety of techniques to minimize the effects of Sun interference. This can include using specialized filters to block out the Sun's light and radio waves, as well as carefully timing observations to avoid periods of high Sun interference. Some telescopes are also designed to physically block the Sun's light from reaching the instrument.

Can Sun Interference be completely eliminated?

While scientists have developed methods to minimize the effects of Sun interference, it cannot be completely eliminated. The Sun is a powerful source of light and radio waves, and its effects can be difficult to fully eliminate. However, with careful planning and specialized equipment, scientists can still gather valuable data even in the presence of Sun interference.

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