Transcript P1 Topic 2 revision flashcards

Q: Who discovered infrared
(IR) radiation?
Q: How did Herschel
discover IR radiation?
Q: Who discovered
ultraviolet (UV) radiation?
Q: How did Ritter discover
UV radiation?
Q: Describe the features of
electromagnetic waves.
Q: List in order the regions
of the continuous
electromagnetic spectrum.
Q: List in order the colours
of the visible light
spectrum.
Q: Describe how frequency
and wavelength changes in
the EM spectrum as we
move from radio waves to
gamma rays.
A: In 1800 he was using thermometers to
investigate the temperature of the different
colours of the visible spectrum (split up
using a triangular prism and projected on a
sccreen). He found that the temperature
increased towards the red end of the
spectrum. To his surprise, the hottest part
was beyond the red end where there was no
visible colour at all. This invisible region is
known as the infrared region.
A: William Herschel (17381822).
A: In 1801 he was experimenting with silver
chloride (AgCl), which turns black when
exposed to sunlight. He placed AgCl in each
colour of the visible spectrum. The rate of
reaction of AgCl increased from red to violet.
He then decided to see what would happen
just beyond the violet end of the visible
spectrum. The rate of reaction of AgCl was
greatest in this invisible region. We know
this region as the ultraviolet region.
A: Johann Ritter (17761810).
A: Radio waves,
microwaves, infrared, visible
light, ultraviolet, X-rays,
gamma rays.
A: All EM waves: are transverse
waves; can travel through a
vacuum; travel at the same speed
of 3 x 108 m/s in air or vacuum;
transfer energy; can be reflected,
refracted and diffracted; obey the
wave equation (v = f x λ).
A: Frequency increases and
wavelength decreases.
A: Red, orange, yellow, green,
blue, indigo, violet.
Q: How does the potential
danger of EM radiation vary
with frequency?
Q: What are the harmful
effects of microwaves?
Q: What are the harmful
effects of IR radiation?
Q: What are the harmful
effects of visible light?
Q: What are the harmful
effects of UV-A radiation
(3.2-4.0 x 10-7 m)?
Q: What are the harmful
effects of UV-B radiation
(2.8-3.2 x 10-7 m)?
Q: What is the benefit to
life of UV-B radiation (2.83.2 x 10-7 m)?
Q: What are the harmful
effects of UV-C radiation (<
2.8 x 10-7 m)?
A: Cause internal heating of
body cells (similar to cooking
food with microwaves). There
have been suggested links with
brain tumours, but nothing has
been proved.
A: The potential danger
increases as the frequency
increases.
A: Intense light can cause
permanent damage to the
retina.
A: Can cause skin burns.
A: Causes sunburn. Can
cause skin cancer and eye
conditions such as cataracts.
Can also destroy proteins in
the eye lens.
A: Causes premature
wrinkling of the skin.
A: This is the most damaging
(ionising); fortunately most
is stopped by the ozone
layer in the atmosphere.
A: Produces vitamin D in the
body.
Q: What are the harmful
effects of X-rays and
gamma rays?
Q: What are the uses of
long-wave radio waves (1-10
km) and why?
Q: What are the uses of
medium- and short-wave
radio waves (sky waves; 10100 m) and why?
Q: What are the uses of very
short-wave radio waves
(space waves; 0.1-10 m) and
why?
Q: Why do you need to be
in direct sight of a
transmitter to receive TV or
FM radio transmissions?
Q: What are the uses of
microwaves?
Q: What are the uses of IR
radiation?
Q: What are the uses of
visible light?
A: Broadcasting and
communications. They can be
transmitted from, say, London,
and received halfway round the
world because long wavelengths
bend around the curved surface of
the Earth. They also get round
around hills, into tunnels etc.
A: Can damage the DNA of
cells. Can cause cell
mutation or destruction.
Can trigger cancer.
A: Broadcasting,
communications and satellite
transmissions. They travel in
straight lines through the
ionosphere to geostationary
satellites, from which they are
re-transmitted back to Earth.
A: Broadcasting an communications.
Can be received at long distances
from the transmitter because they
are reflected off the ionosphere – an
electrically charged layer in the
Earth’s upper atmosphere,
depending on atmospheric
conditions and time of day.
A: Cooking, communications
(e.g. mobile phones) and
satellite transmissions.
A: The signal cannot bend
around hills or travel far
through buildings.
A: Vision, photography,
illumination.
A: Cooking, thermal imaging
(thermographs), short-range
communications (e.g. cordless
computer mouse), remote
controls, optical fibres, security
systems.
Q: What are the uses of UV
radiation?
Q: What are the uses of Xrays?
Q: What are the uses of
gamma rays?
Q: What is ionisation?
Q: When do radioactive
sources emit ionising
radiation?
Q: Which are the ionising
radiations?
Q: What is the nature of
alpha and beta radiation?
Q: How is ionising radiation
detected?
A: Observing the internal
structure of objects, airport
security scanners, medical
X-rays.
A: Security marking,
fluorescent lamps, detecting
forged bank notes,
disinfecting water.
A: A process in which
radiation transfers some or
all of its energy to liberate
an electron from an atom.
A: Sterilising food and
medical equipment, the
detection and treatment of
cancer.
A: Ultraviolet, X-rays,
gamma rays, beta particles
and alpha particles.
A: All the time.
A: Using a Geiger-Mϋller (GM) tube. A
single alpha or beta particle entering the
tube causes the gas atoms inside the tube
to ionise. This produces a burst of
electrical charge, which is detected by the
counter connected to the GM tube. Each
‘clicking sound’ or ‘count’ represents the
detection of a single particle.
A: Alpha particles (identified by
Ernest Rutherford in 1907 as
high-speed helium nuclei) and
beta particles (identified as
high speed electrons in 1898
by Fritz Geisel, Henri Becquerel
and Marie Curie).