Radiation Exposure from flying

Thats if freq were to = wavelength, but there is also the velocity of the wave to consider also…
http://www.gcse.com/waves/wave_speed.htm

http://en.wikipedia.org/wiki/Wavelength

Ahh… OK, I stand corrected. Luckily for me as a sound engineer the only variable I have to think about relating to the speed of sound waves is air temperature!

Paul

Thats if freq were to = wavelength, but there is also the velocity of the wave to consider also…

The frequency of a set of waves is set at the source itself. For instance, if Billy pokes a pond with a stick twice each second, the frequency will be 2 Hz.

As the waves travel over the pond’s surface, this frequency will not change. What may change is the distance between waves – the wavelength – and their speed.

http://www.gcse.com/waves/wave_speed.htm

When light waves (and other electromagnetic waves) enter a medium, their wavelength is reduced by a factor equal to the refractive index n of the medium but the frequency of the wave is unchanged.

http://en.wikipedia.org/wiki/Wavelength

So because the speed changes, the wavelength must change to keep freq const.

But that’s impossible! You can not change the wavelength of a wave without affecting the frequency! If you double the frequency of a wave you halve the wavelength, they have a perfect inverse relationship. That’s just how waves work, whether they’re light, sound or water waves!

This is getting more confusing by the hour! 😀

Paul

wow I thought I had escaped from physics until September!

Well thanks for answering my question bout the radiation ….. learn something new everyday!

Thanks for the lesson……as yes, I think it is the frequency that changes not the wavelength 🙂 Don’t know how I’ve gotten this far in my education :rolleyes: :p

Why would bending light change its frequency? (And therefore wavelength also, as you can’t change one without changing the other).

So because the speed changes, the wavelength must change to keep freq const. Wikipedia: http://en.wikipedia.org/wiki/Wavelength

So back to civ aviation 😀 I think the best form of radtion you can get in flight is the view of the aurora borealis

Because wave energy travels at different speeds in different mediums. Velocity of the wave ‘v’ vaires with the frequency ‘f’ multiplied by the wavelength ‘lambda’ (v=f x lambda). Therefore when the velocity of the wave is changed the frequency will alter to keep the wavelength constant.

I know I’m probably being really stupid here, but I’m not entirely sure what you mean when you say ‘the frequency will alter to keep the wavelength constant’.

My understanding of what you’re saying is that when a light wave slows down, to keep its wavelength constant (i.e. To keep the colour the same) the frequency changes, but changing the fequency would change the colour anyway, as wavelength is just the distance between complete cycles, and the number of cycles is frequency dependant. Surely it defies the laws of physics to be able to change the frequency of a wave but not its wavelength?!

I’m konfuzde… :confused:

Apologies for turning this into a physics lesson. I’m just curious, and not knowing silly little things like this bugs me!

Paul

…Whats next radiation badges for crew? :p

Actually Andrew we sort of have these already!!! Virgin and most of the serious airlines have radiation monitoring programs. The recommended maximum annual dose is 20 milliSieverts. Virgin sets a company max annual dose of 6 milliSieverts and our rosters are arranged so that we do not exceed that amount. The highest dose route is LHR-NRT as that takes us closest to the North Pole. The Earths magnetic field and thinness of the atmosphere at the poles causes the least protection in these places. As we have Japanese crew members who solely do the Tokyo run these guys and girls are the highest risk employees in the company. Consequently you will sometimes find Japanese crew members on the Joburg route (the least risk) so that the company can still get productivity from them without having to ground them for reaching their annual radiation limit.

By the way, I average 3 trips (6 sectors) a month and typically go transatlantic once every other month. Our 747 bods go transatlantic every time they get off the ground (poor boys!).

Because wave energy travels at different speeds in different mediums. Velocity of the wave ‘v’ vaires with the frequency ‘f’ multiplied by the wavelength ‘lambda’ (v=f x lambda). Therefore when the velocity of the wave is changed the frequency will alter to keep the wavelength constant.

When they say you are exposed to ‘more radiation’ when flying, they may be taking into account the radiation given off by sitting around all the electircal equipment for around 10 hours, plus radiation given off by your fellow passengers……who knows where they are getting their figures from.

If it was that big a deal I’d imagine a lot more fuss would be made about people using air travel :rolleyes:

.Another factor is that when any form of light passes through glass,it refracts(bends),therefore changing the wavelength & frequency further reducing it’s power.

Why would bending light change its frequency? :confused: (And therefore wavelength also, as you can’t change one without changing the other).

Paul

Longhaul fly about 4 – 5 times a month. A trip could be 3 days or longer if they dont have a daily service. For example MYT A330 crews spend a week in some places as they are only flown once a week. I think max is 10-12 hours without a relief crew but usually anything over 9hrs there is a third person. Such as Virgin to SFO from LHR is 2 First Officers and a Captain.

Whats next radiation badges for crew? :p

“So apparently one flight across the atlantic recieves the same amount of radation as an x-ray”.

A few problems with that statement, x-rays are much stronger then the UV(ulta-violet) rays that come off the sun,UV rays lack the power to penetrate through metal(i.e an aircraft fuselage),so a few hours of UV exposure is not the same as a few minutes/seconds of x-ray exposure.Another factor is that when any form of light passes through glass,it refracts(bends),therefore changing the wavelength & frequency further reducing it’s power.To sum up this is a bit of myth & that no amount of flying will in anyway cause the same effects of x-rays,the sun simply doesn’t produce that kind of radiation on earth.

erm Friday 16th June?

Yes.

Might be a bit of a stupid question bout approx how many times would a BA/AA/VS etc pilot cross the atlantic a week?

I’d say about 3 or 4 times, although I have no idea what a crew roster for those airlines would look like.

I must have done the same exam as you:). Yep, as A330-300 says, but the dose of background radiation is only a tiny bit higher at 30000ft than on the ground, so little harm is likely to occur but I suppose it is a good example for an exam board to use.

erm Friday 16th June?

Cheers for that! Might be a bit of a stupid question bout approx how many times would a BA/AA/VS etc pilot cross the atlantic a week?

I must have done the same exam as you:). Yep, as A330-300 says, but the dose of background radiation is only a tiny bit higher at 30000ft than on the ground, so little harm is likely to occur but I suppose it is a good example for an exam board to use.

Yep, it’s true, someone at college mentioned it.