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4.3 WAVES (characteristics) (:star:POLARIZATION :star: (transverse waves,…
4.3 WAVES (characteristics)
WAVEFRONTS
surfaces through crests
normal to the direction of energy transfer
RAYS
:
lines in the direction of energy transfer
normal to the wavefronts
INTENSITY, I
:
directly proportional
square of the
amplitude
energy of the wave
directly proportional
square of the
amplitude
I ∝A²
I = Power/area
Wm‾²
SUPERPOSITION
:explode:
2 or more waves of the same type
a given point in space at the same time
the displacement of the medium at that point
algebraic
sum of individual displacements
y=y₁ +y₂
y₁ and y₂ are individual displacements
a
pulse
created in a rope with one end fixed
a
fixed end
Newton's 3rd Law
exerts an equal but opposite force on the rope
the pulse is reflected by the wall and inverted
a wall
a phase change
180° when reflected
a
free end
the pulse moving in the opposite direction
not inverted
no phase change
a
positive
and
negative
pulse superpose
cancel each other out
totally overlap
the rope looks flat
it is moving
:star:
POLARIZATION
:star:
transverse waves
2 types of oscillations is perpendicular
the direction of propagation
many modes
electric field
electromagnetic wave
the electric field
electromagnetic wave
the same plane
passing it through a
polariser
vertical transmission axis
in the path of unpolarised light
transmit only vertically polarised light
REFLECTION
from a non-metallic surface
the reflected ray is
partially polarised
the reflected light
various components
electric field of unequal magnitude
partially horizontally polarised
'glare' from the reflections
wearing Polaroid sunglasses
vertical transmission axes
MALUS'S LAW
how the intensity of polarised light
by a 2nd polariser (analyser)
I = Iₒ cos²ϴ
ϴ is the angle between the plane of polarisation
the transmission axis of the polariser
how much the intensity of transmitted light is reduced
the 2nd polariser
Iₒ is the incident intensity
I is the intensity of light
have
which are
and
which are
and
also have
which is
to the
hence
because
is also
to the
is defined as
with unit
happens when
arrive at
hence
is the
for example, when
they
has the value
where
when they
hence
but
when
approaches
it experiences
for example
the wall
hence
of
there is
is
undergo
occurs only in
because
to
for example
in an
happens when
in an
oscillates on the
occurs by
with a
placed
hence it will
may be achieved by
when this happens
which means
has
of
or
produce
can be reduced by
which have
tells
is affected
is defined as
where
and
determines
by
