2.5 ENERGY TRANSFER 2
Learning Objectives:
Describe some sources of infrared radiation.
Explain how energy is transferred by radiation.
Quick recap:
What are the two methods of
heat transfer we have learned
about so far?
Can you explain what’s happening
in terms of particles?
There are three methods of heat transfer:
Yesterday’s
lesson
Today’s lesson
RADIATION is a way of transferring
heat, which does not need particles. The
sun’s energy reaches the earth by
radiation.
Heat radiation from the sun is called
SOLAR RADIATION or RADIANT HEAT.
Radiation travels in straight lines.
This is called a radiator
because it radiates heat.
ABSORBS heat radiation, the
When an object _________
heat energy is transferred to the object. The
object heats up.
REFLECTS heat radiation, the
When an object _________
heat energy bounces off the object and is not
transferred to the object. The object does not
heat up.
EMITS heat radiation, heat
When an object _________
from the object is transferred to the
surroundings.
The more heat radiation is absorbed by an
object, the hotter the object gets.
Different types of surface absorb different
amounts of heat.
Pale or silver surfaces DO
NOT absorb much heat
radiation, because they
reflect heat radiation well.
They also don’t emit heat
radiation very well.
Why do you think marathon
runners are given silver
blankets after the race?
How do you think cricket
players keep cool by wearing
white?
Why do you think some
buildings in hot countries are
painted white?
Dark, dull surfaces absorb
heat radiation well.
They also emit heat radiation
well.
They do not reflect heat
radiation very well.
Why do you think the inside
of an oven is painted black,
not white?
Why do you think cats
prefer sleeping on black cars
than white cars?
So, what do you think is going to happen in our
experiment?
Shiny or pale
surfaces
Dull or dark
surfaces
Good absorbers
of heat?
NO
YES
Good emitters of
heat?
NO
YES
Good reflectors
of heat?
YES
NO
Now you should take a new
page in your book and
prepare a large summary of
conduction, convection and
radiation. Include diagrams!
HOMEWORK:
Complete the conduction, convection and
radiation worksheet.
Hand in just the sheet.
http://www.teachertube.com/video/radiationconduction-and-convection-159713