Waves and Lenses - Physics Paper 2 Flashcards
What is a wave?
An oscillation that transfers energy without transferring any matter
What is an oscillation?
A vibration
What is a transverse wave?
Waves that oscillate 90 degrees to the direction of energy transfer of the wave
What are some examples of transverse waves?
light , EM waves, ripples on water and waves on strings or springs when they are wiggled up and down
What is a longitudinal wave?
A wave that oscillates parallel to the direction of energy transfer of the wave
What are examples of longitudinal waves?
sound waves
Do waves transfer matter?
No, only energy
What is the rest position of a wave?
the undisturbed position of particles or fields when they are not vibrating
What is a wave’s displacement?
the distance that a certain point in the medium has moved from its rest position
What is the peak or the crest of a wave?
the highest point above the wave’s rest position
What is the trough of a wave?
the lowest point below the wave’s rest position
What is the amplitude?
the maximum displacement of a point on a wave from its rest position
What is the wavelength of a wave?
the distance between the same point on 2 adjacent waves
What is the wavelength of a transverse wave?
the distance between the crest of one wave and the crest of the next wave
What is the frequency of a wave?
the number of waves passing a point each second
What is frequency measured in ?
Hz
What is the period of a wave?
The amount of time it takes for a full cycle of the wave to be completed
What are the units for a period?
Seconds
What is the equation for calculating the period?
period = 1 / frequency
What is the wave speed?
The speed at which a wave is moving and energy is being transferred
What is the equation for wave speed?
wave speed = frequency X wavelength
What are the units for wavespeed?
m/s
What are the units for wavelenght?
Metres
What 3 things can happen when a wave meets a boundary?
A wave can be absorbed, reflected, or transmitted
What happens if a wave hits a boundary at an angle?
It’s refracted
What is the normal?
A straight line that is at 90 degrees to the boundary
What happens if a ray travels along the normal and hits the boundary at 90 degrees?
The ray will pass through the boundary without changing direction and the angles of incidence and refraction will both be 0 degrees
What is the optical density of a material?
A measure of how quickly light travels through a material
The higher the optical density….
the slower light travels
What is the refractive index?
A measure of a material’s optical density
The bigger the refractive index…
the more optically dense a material is.
What are wavEfronts?
Imaginary lines drawn through certain points on waves. They’ re perpendicular to the direction in which the wave is moving
What happens if a wave slows down at a boundary?
It bends towards the normal
What happens if a wave speeds up at a boundary?
It bends away from the normal
What happens if a wave enters a more optically dense material?
The wave moves more slowly in the new material and bends towards the normal. The angle of refraction will be smaller than the angle of incidence.
What happens if a wave enters a less optically dense material?
The wave moves faster in the new material and bends away from the normal. The angle of refraction will be greater than the angle of incidence.
What does the law of reflection state?
That the angle of incidence = the angle of reflection
What are the different types of reflection?
Specular and diffuse
What is specular reflection?
Where parallel lines are reflected in a single direction by a smooth surface
What is diffuse reflection?
Where parallel lines are reflected by a rough surface and the reflected rays are scattered in lots of different directions
Why is the angle of incidence different for each ray in diffuse reflection?
Because the tiny bumps on the surface mean that the normal for each ray is different. Therefore, the angle of incidence is different for each ray.
What is the EM spectrum?
a continuous spectrum of all the possible wavelengths of EM waves
Are EM waves transverse or longitudinal?
Transverse
What are all the EM waves in order of increasing frequency?
Radio waves, microwaves, infrared, visible light, ultraviolet light, X-rays, gamma rays
What is the speed of EM waves in a vacuum?
3 X 10^8 m/s
What do longitudinal waves require to travel in?
A medium
What is the human hearing range?
20Hz to 20,000 Hz
Does the frequency change when a wave changes medium?
No
high frequency sound has what pitch/
A high pitch
the higher the amplitude…
the louder the sound
sound waves can only move through what?
A medium as they need to vibrate
what is a reflected sound wave called?
An echo
crust…
mantle, outer core, inner core
Why does an earthquake happen?
due to the sudden movement between the tectonic plates in the earth’s crust. seismic waves carry energy away from the earthquake , which pass through the earth
what are the 2 types of seismic waves?
p waves and s waves
What type of waves are p waves?
p waves are longitudinal waves
What type of waves are s waves?
s waves are transverse waves
