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Green Flash

Extracts from this document...

Introduction

Physics

July 6

2007

Green Flash at Sunset

By Sarah Nader


Table of contents

Title

Page

Cover page

1

Table of contents

2

Introduction

3

What is a green flash?
Types of green flashes.

4
4

How do they occur? – The basics
                      Atmospheric Inversion
                     Refraction
                    Speed of light & colours

5
5
5
6

How do they occur? – Putting it all together
                   
What are they best conditions for them to occur?

7
7

Conclusion

8

References

9


Introduction

One day, you may have heard that there was a phenomenon called a ‘green flash’ or you might’ve come across it in the recently released third Pirates of the Caribbean movie which represents it as an indication that a soul has returned to the land of the living. After hearing about it, you might’ve wondered if it actually was real and if it was, how does it occur? Through the next pages you’ll find the answers to your questions and learn how it works through physics.


On a side note, you should realise that the ‘green flash’ is not an indication that a soul has returned to the land of living, as represented in Pirates of the Caribbean.


What is a green flash?


The green flash is a rare optical phenomenon that occurs shortly before sunrise or after sunset. Despite its name, there is no actual flash, rather it’s more just like a spot of green above the sunset point or green rays that shoot up from the sunset/sunrise point.

Types of green flashes.

...read more.

Middle

Inversion layers block the upward movement of air, effectively trapping pollution (such as smog) close to the surface of the Earth. By suppressing convection currents, violent thunderstorms can evolve if any moisture is present.

Refraction
Refraction is the change in direction of a ray of light as it passes obliquely from on medium into another[2](mediums must have different optical densities).In this case, refraction occurs because of the differences in the atmospheric layers (temperature and density) and allows for optical phenomena such as mirages, Fata Morgana (objects on the horizon appear elongated and elevated) and others to occur. Some well known visual distortions caused by the atmospheric refraction of light are as follows:

  • Stars in the sky appear higher than they actually are (see Figure 1[3])                                             apparent position of star
  • The setting sun is visible after it has                                                                                true position
    actually gone over the horizon and                                                                        
    its shape appears slightly flattened
  • Stars appear to twinkle due to the
    varying refractions of light from the
    star as it passes through the atmosphere.

Figure 1 shows that as light travels from the star to the observer, it is bent accordingly (although quite exaggerated in the diagram) to the varying optical densities of the different layers of the atmosphere.  In the atmosphere, objects are refracted the most when they are lower in the

...read more.

Conclusion

Conclusion

The ‘green flash’, though it has only been spotted several times, is a very rare occurrence but, most importantly, we’ve find out that it is real and does happen, although it is only seen by people that know what they’re looking for (or are very, very lucky). The ‘green flash’ occurs because of various physics concepts such as refraction, the speed of light and others, similar to other optical phenomena occurring in the atmosphere.


References

Bilbiography

Author

Date

Title

Web Address

Joe Wolfe

23/06/07

“Green Flash”

http://www.phys.unsw.edu.au/~jw/greenflash.html

-

23/06/07

“Green Flash”

http://en.wikipedia.org/wiki/Green_flash#Types_of_green_flashes

-

24/06/07

“Fata Morgana”

http://en.wikipedia.org/wiki/Fata_Morgana_%28mirage%29

-

24/06/07

“Atmospheric “Inversion”

http://science.enotes.com/earth-science/atmospheric-inversion-layers

-

30/06/07

“Green Flash”

http://www.mtwilson.edu/vir/parkinglot/greenflash/

-

30/06/07

“Green Flash”

http://www.meteoros.de/flash/flashe.htm

Dave Thurlow

30/06/07

“Green Flash”

http://www.weathernotebook.org/transcripts/1999/09/29.html

Books

CAHILL, J

1998

Heinemann Physics for Western Australia 11

Melbourne, Heinemann

LUCARELLI, M
HENDERSON, T

2001

Year 11 Study Guide - Physics

-, Academic Associates


[1] Definition obtained from ‘http://wordnet.princeton.edu/perl/webwn?s=anomaly’

[2] Obtained from page 47 of the Heinemann Physics for Western Australia 11 by Jeff Cahill

[3] Figure 1 is modeled after the diagram on page 47 of the Heinemann Physics for Western Australia 11 by Jeff Cahill.

[4] Sentence partially obtained from page 56 of the Heinemann Physics for Western Australia 11 by Jeff Cahill.

[5] Diagram modeled after the diagram by Joe Wolfe at http://www.phys.unsw.edu.au/~jw/greenflash.html

...read more.

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