C/W 2 nd November 2011 Microwaves Keywords: absorb microwave sample bias Objectives: Must –...
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Transcript of C/W 2 nd November 2011 Microwaves Keywords: absorb microwave sample bias Objectives: Must –...
C/W 2nd November 2011
Microwaves Keywords: absorb microwave sample bias
Objectives:Must – Understand the heating effects of radiation can damage cellsShould – Know what microwaves can be used for. Could – Understand how risks can be assessed.
Starter Why do microwave ovens cook potatoes but our phones don’t cook our heads? Write down 3 reasons in the back of your book.•Microwave ovens are more intense•Microwave ovens are on for longer•Microwave ovens use a grater (or higher) frequency (so more energy)
HHo
What type of electromagnetic wave would a paper clip in a plug produce?In P3 we will learn that mains electricity has a frequency of 50Hz
So 50 Hz radio waves.
C/W 3rd November 2011
Ozone Keywords: ozone
Objectives:Must – Understand that ozone protects living organisms Should – Know whether to accept different risks
Electromagnetic Spectrum
Radio
Micro
Infra-Red
Light
Ultra-V
iolet
X rays
Gam
ma
Wavelength () increases
Can you think of a phrase that would help you remember this order? Gate X Usually Lets In Most Radiation
High frequency
Short wavelength
High energy
Most penetrating
High frequency
Short wavelength
High energy
Most penetrating
Low frequency
Long wavelength
Low energy
Least penetrating
Low frequency
Long wavelength
Low energy
Least penetratingx
UV radiation Produced by the sun the 3rd highest energy after X-rays and gamma rays. So can be dangerous.
We can also get UV lamps......
UV can be dangerous does anything protect us?
Thomas Midgley, Jr.
Despite good intensions this chemist had a complete mare!
1st he introduced leaded petrol....
Then using CFC’s in fridges......
These two developments had very serious negative effects on the environment.
Ozone protects us from some of the Suns UV rays., by absorbing them
Ozone sheet
This picture shows the hole in the ozone layer
Why is this hole a problem?
Write down 2 reasons in your book.
1) Ice caps melt2) More chance of skin cancer
•Higher level !•How is ozone made? •Ozone is made when high energy UV radiation from the sun are absorbed by oxygen molecules and they react together making O3
• Ozone can react with other molecules like nitrogen, hydrogen, bromine and chlorine compounds. Which changes this part of the atmosphere.
Subheading - How can we protect ourselves from UV radiation?
-sun cream -Cloths
-Complete book problems page 246
H
Plenary
Tell your partner one thing you have learnt today, then swap, then tell somebody else. I will ask you what they have learnt!
Boswells physics blog
http://boswellsphysics.blogspot.com/
http://www.youtube.com/watch?v=Ws6AAhTw7RA
C/W 3rd November 2011
Ozone Keywords: ozone
Objectives:Must – Understand that ozone protects living organisms Should – Know whether to accept different risks