[Catalist] Channel 9 News this afternoon

Tue Nov 27 12:20:06 AEDT 2018

White, or ivory tuskan cream BMW bodies under those conditions would be hot to touch (big vibrations of bodies' atoms due to incident focussed EMR). Black BMW bodies would be hotter to touch due to being better absorbers of EMR(agreed), but they're also better radiators. The building would've acted like a concave mirror with a long-ish focal length, not a lens, nor a magnifying glass. So, I would get my students to model the activity with concave mirrors. Then we'll make a solar bbq, with our big concave mirror, after determining its focal length, and cook one white chicken sausage and one dark sausage, a la black pudding, and share it around. We might even stick temperature probes into the two sausages via a Vernier data platform. Bon Appétit!

-----Original Message-----
From: Catalist [mailto:catalist-bounces at lists.stawa.net] On Behalf Of Ray Forma
Sent: Tuesday, 27 November 2018 8:53 AM
To: WA Science Teachers Discussion List
Subject: Re: [Catalist] Channel 9 News this afternoon

‘Morning all,

at this time of year when it’s a bright day get your students to put spots of various colours on the whitest paper you can find. Definitely use at least one ‘light’ colour like bright yellow. Then give them a magnifying glass, a stopwatch, and take them into sunlight. Show them how to focus a sun image on the paper. Then get them to time how long it takes for each colour to char under the Sun’s image. Include the time taken for a patch of the white to char. Note: have some water available in case the whole sheet catches fire.

Normal students are always amazed by the different times. Remind them that the yellow spot is absorbing all of the incoming spectrum other than the small range of yellow radiation. The black spot absorbs close to 100% of incoming radiation. Because energy is never destroyed or created anywhere except in nuclear reactions, the colours convert the absorbed radiation into internal energy (= heat for ordinary folk).

The same applies to car surface colours.

Note that ‘white’ cars are seldom white; most are a shade of cream. Illustrate that by checking the charring time of very “white" paper compared with ordinary “white” paper such as newsprint. That opens up the field of whiteness vs brightness <https://apac01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreativepro.com%2Fpaper-tips-confused-over-brightness-and-whiteness%2F&data=02%7C01%7Cferdinand.nicoletti%40education.wa.edu.au%7C61626b27ded240f8f56408d654030c64%7Ce08016f9d1fd4cbb83b0b76eb4361627%7C0%7C0%7C636788769422128476&sdata=recOptMgJ3T%2Fm9Vj81QQ0xJZ3tf26nSraUNhNrAoa2Y%3D&reserved=0>. Your students may end up in office-work, creative industries, marketing, and advertising, where understanding these concepts is relevant.

However, this is not in the curriculum, so don’t waste time on it.

> On 26 Nov 2018, at 13:32, NICOLETTI Ferdinand [Como Secondary College] <Ferdinand.Nicoletti at education.wa.edu.au> wrote:
> 
> The shape and reflectivity of the glass building, acting as a concave mirror would have focussed and, hence, intensified the sunlight to a focal region on-and-aroundthe black car. Under those conditions white BMWs’ bodies would also be too hot to touch.
> 
>  
> 
> From: Catalist [mailto:catalist-bounces at lists.stawa.net] On Behalf Of leon at quoll.com
> Sent: Monday, 26 November 2018 1:11 PM
> To: WA Science Teachers Discussion List
> Subject: Re: [Catalist] Channel 9 News this afternoon
> 
>  
> 
> And the rest Warren, flame temperatures get to nearly 1900K. Quite clearly not just IR, although most of the power will be in those wavelengths.
> 
>  
> 
> Black is not necessarily black in ir, but usually is, as anyone who has used a soldering iron will tell you. It is good to note the distinction though.
> 
>  
> 
> Cheers, Leon
> 
>  
> 
> -------- Original message --------
> 
> From: Warren Stannard <warren.stannard at uwa.edu.au>
> 
> Date: 26/11/18 11:57 am (GMT+08:00)
> 
> To: 'WA Science Teachers Discussion List' <catalist at lists.stawa.net>
> 
> Subject: Re: [Catalist] Channel 9 News this afternoon
> 
>  
> 
> Hi Ray... Not sure I agree with some of your conclusions. A forest fire will, I think, reach temperatures of about 600K which is still in the infra-red region of the spectrum. . Most painted surfaces in this region of the spectrum will
> Cheers
> Warren Stannard
> 
> -----Original Message-----
> From: Catalist <catalist-bounces at lists.stawa.net> On Behalf Of Ray Forma
> Sent: Thursday, 22 November 2018 8:10 PM
> To: WA Science Teachers Discussion List <catalist at lists.stawa.net>
> Subject: Re: [Catalist] Channel 9 News this afternoon
> 
> Another example of someone silly enough to buy a black car in Western Australian conditions. People who do so need to find their physics teacher and ask for their money back.
> 
> As a voluntary firefighter I’ve come across many examples of black or coloured objects absorbing enough radiant energy to reach ignition.
> 
> In the Margaret River fire houses burned down because:
> 
> 1 Black vinyl barbecue covers on second-floor verandas catching fire & setting the wooden veranda ceiling on fire, then the rest of the place
> 
> 2 Black pillows on a couch smouldering. Luckily we spotted them, broke the window, and threw them into the ashbed of the garden
> 
> 3 Rubber outside doormats catching fire and burning long enough to set the door on fire, then the rest of the house. Why have outside doormats in a fire-prone area?
> 
> 4 Non-white curtains caught fire because the owners did not think about thoroughly dousing them with water. They then set the rest of the place on fire.
> 
> In the Victorian bushfires many victims were roasted in their cars after crashing into fallen trees or each other in the smoke. Of those who didn’t crash, 100% of the white cars made it to safety. Not so the coloured ones.
> 
> > On 22 Nov 2018, at 14:17, John Clarke <john at stawa.net> wrote:
> > 
> > Hi All,
> > 
> > Keep an eye on the Channel 9 news this afternoon at 4:00 or 6:00pm. Lance Taylor and I are part of the follow up story about the problem they had with the Woodside building causing a car to almost burn yesterday.
> > 
> >  
> > 
> > The link to yesterday’s story.
> > 
> > https://apac01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.9news.com.au%2Fnational%2F2018%2F11%2F21%2F21%2F41%2Fcar-catches-alight-in-perth-cbd-from-reflection-of-office-building&data=02%7C01%7Cferdinand.nicoletti%40education.wa.edu.au%7C61626b27ded240f8f56408d654030c64%7Ce08016f9d1fd4cbb83b0b76eb4361627%7C0%7C0%7C636788769422138480&sdata=GgWmtHbBqe6X8c2%2FGwAJBQKroaRPiitznS%2FIQLQvd7E%3D&reserved=0
> > 
> >  
> > 
> > Regards,
> > 
> > John
> > 
> >  
> > 
> > John Clarke
> > 
> > CEO
> > 
> > STAWA
> > 
> > Unit 6/1270-1274 Albany Highway
> > 
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> Regards,
> 
> Ray Forma
> Tel +61 (0) 428 596 938
> 
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Regards,

Ray Forma
Tel +61 (0) 428 596 938

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