section 3 Flashcards
waves
what is a wave? 1 marker version
a wave is the oscillation of particles or fields
what is a progressive wave?
a progressive (moving) wave carries energy from one place to another without transferring matter
what’s a wave cycle?
one complete oscillation(vibration) of the wave
displacement of a wave , m
how far a point on the wave has moved from its undisturbed position.
Amplitude, m
The maximum displacement from, the equilibrium
wavelength, m
the distance between adjacent points that oscillate in phase
time period , s
The time taken for one complete oscillation to pass a given point
frequency ,Hz
The number of cycles per secound passing a given point
Path difference
the difference in distance travelled by two waves to reach a given point.
phase difference
Phase difference is a measure of the difference in where two waves are in their cycle.
what is superposition?
the displacement of the resultant wave which is the sum of the displacement of the individual waves.
What is diffraction?
its the spreading out of waves when going through a gap.
constructive interference
occurs when 2 waves have displacement in the same
direction (in phase)
destructive interference
occurs when one wave has positive displacement and the other
has negative displacement, if the waves have equal but opposite displacements, total destructive interference occurs (anti-phase)
define coherence
coherent waves have a fixed phase difference and same frequency and wavelength.
what is monochromatic ?
light with the same wavelength(and frequency) therefore same colour.
Which one : blue light or red light refract more or less
Blue light refracts more
Red light refracts less
( it’s the opposite for diffraction
Light is shone through a single narrow slit, create an a diffraction pattern on a screen. How does the central maximum of the diffraction pattern change when the width of the slit is increased?
The central maximum becomes narrower and its intensity increases
What are optical fibres used for?
Optical fibres are used to transmit digital signals.
What issue can occur with digital signals in optical fibres?
Digital signals can suffer from degradation.
What are the types of signal degradation in optical fibres?
Types of signal degradation include attenuation and dispersion.
What causes attenuation in optical fibres?
Attenuation is caused by absorption and scattering of light.
What causes dispersion in optical fibres?
Dispersion is caused by different light wavelengths traveling at different speeds.
how can a ray enter a prism with out any deviation?
it has to enter through the normal line /perpendicular to the boundary to the prism
when changing orders in a diffraction grating what do we consider?
we always check order at 90 degrees using n lambda=sin theta
Visible light ROYGBIV
RED ORANGE YELLOW GREEN BLUE INDIGO VIOLET(PURPLE) IN ORDER FROM SMALLEST (red 700nm to violet 380 nm).
