Page 2 - Topic 3
P. 2
CONCEPT CHECK – WAVE BEHAVIOUR minima or maxima on the screen, and
is the slit-to-screen distance.
L
OF LIGHT
The interference pattern produced
DO YOU KNOW? by light passing through a
transmission diffraction grating
Concept While Before demonstrates the wave behaviour of
studying the light.
test
Transmission diffraction gratings can
Oscillating charges produce be used to analyse the spectra of
electromagnetic waves of the same various light sources.
frequency as the oscillation;
electromagnetic waves cause
charges to oscillate at the frequency
of the wave. CAN YOU?
Electromagnetic waves are Application While Before
transverse waves made up of Studying the test
mutually perpendicular, oscillating
electric and magnetic fields. • Use the frequency of
oscillation of the electrons in
The speed of a wave, its frequency, the transmitting and receiving
and its wavelength are related antennae to explain the
through the formula v = f λ . transmission and reception of
radio or television signals.
Monochromatic light is light • Relate the orientation of the
composed of a single frequency. receiving antenna to the plane
Most light sources emit waves that of polarisation of radio or
radiate in all directions away from the television waves.
source. • Solve problems using v =
f λ .
Coherent wave sources are wave
sources that maintain a constant • Describe what is meant by
phase relationship with each other. two wave sources being in
phase or out of phase.
When two or more electromagnetic • Explain why light from an
waves overlap, the resultant electric incandescent source is neither
and magnetic fields at a point can be coherent nor monochromatic.
determined using the principle of
superposition. • Use the principle of
superposition to describe and
When the waves at a point are in represent constructive and
phase, ‘constructive interference’ destructive interference.
occurs. • Use the principle of
When the waves at a point are out of superposition to determine
phase, ‘destructive interference’ points of maximum or
occurs. minimum amplitude resulting
from the interference of light
For two monochromatic sources in from two wave sources of the
phase, the waves at a point some same frequency.
distance away in a vacuum: • Use constructive and
− constructively interfere when the destructive interference to
path difference from the sources explain the maximum and
to the point is mλ minimum amplitudes.
− destructively interfere when the • Describe how two-slit
path difference from the sources interference is produced in
to the point is (m + 1 ) λ the laboratory using a
2 coherent light source or using
where m is an integer and λ is the a single slit between a light
wavelength. source and the double slit.
• Describe how diffraction of
Young’s double-slit experiment can the light by the slits in a two-
be used to demonstrate the wave slit interference apparatus
behaviour of light. allows the light to overlap and
The formulae sind θ m and hence interfere.
λ =
λ L • Sketch a graph of the intensity
∆ y = can be used to analyse the distribution for two-slit
d
interference pattern, where d is the interference of
monochromatic light.
distance between the slits, θ is the (Consider only cases where
angular position of the maximum, the slit separation is much
∆ y is the distance between adjacent
