A wave is a pattern of movement that transfers
energy. E.G. if you drop a twig into a pool, ripples
of the water form on the surface.
Transverse
E.G. waves in water
and waves on a rope
Longitudinal
They squash up and stretch
out the arrangement of
particles, making
compressions ((high pressure,
lots of particles) and
rarefactions (low pressure,
fewer particles)
Wave
Speed
Equation
Wave speed (m/s) = Frequency (Hz) x
Wavelength (m)
Reflection &
Refraction
Waves
are
Absorbed
By the second material - its
energy is transferred to the
material, causing heating.
Waves are
Transmitted
Through the second
material - wave carries
on travelling through the
new material, leading to
refraction
Waves are
Reflected
It is sent away
from the second
material.
Changing
Direction at a
Boundary
Waves travel at different speeds in different
materials, so when one crosses a boundary
between materials it changes speeds. The
frequency of it stays the same as it crosses a
boundary. If the speed changes, the
wavelength must change too. The greater the
change in speed, the more a wave bends.
Electromagnetic
Spectrum
How the EM
Waves are
Emitted
Changes in nuclei can cause
gamma rays to emit.
Visible, UV and X-rays are
emitted when electron drop
down energy levels
Uses of EM
Radiation
Radio waves are used for
communication and transmit
information like radio shows from
one place to another.
Microwaves are
used for cooking and
communication
Infrared is used to
increase/monitor
temperatures
UV lamps are used
in tanning bed.
X-rays are used
in hospitals to
see inside the
body.
Gamma radiation is
used in cancer
treatments (to kill
the cancer cells)
Energy Levels
and Ionisation
An atom is ionised if
it loses an electron
Ionising radiation
harms living cells
Absorbing &
Emitting Radiation
Radiation Affects
the Earth's
Temperature
During the day, lot of EM
radiation is transferred to the
Earth from the Sun and the
atmosphere allows some of it to
pass through to be absorbed by
the Earth's Surface, which
warms it and causes an increase
in the temperature. At night, less
EM radiation is being absorbed
than is being emitted, causing a
decrease in the temperature. So,
the temperature of the Earth
stays constant.