Section 4 - Properties Of Waves Flashcards
What is a wave?
Wave transfers energy in the direction of travel
What is the equation for wave speed?
V=f x wavelength
Describe a transverse wave?
A wave that vibrates perpendicular to the direction of travel
What are some examples of transverse waves?
All light and electromagnetic radiation
What is amplitude?
The maximum displacement of a point on a wave from into undisturbed position
What is wavelength?
The distance between the same point on two adjacent waves
What is frequency?
The number of complete waves that pass a certain point per second
Describe a longitudinal wave
A wave that vibrates parallel to the direction of travel
What is an example of a longitudinal wave?
Sound waves
What is wave speed?
Is the speed at which energy is being transferred
What is reflection?
Reflection is when a wave bounces off a surface
What is the law of reflection?
The law of reflection states that the angle of incidence always equals the angle of reflection
How can reflection be shown using water waves
In a ripple tank a dipper will create waves, when a barrier is places the waves will be reflected
What are the two shoes of reflection and explain them
Diffuse - when the light hits a bumpy surface and the image is unclear
Spectral - when the light hits a flat surface and the image is clear
What is refraction?
When waves change direction when passing from one medium to another
Why do waves travel differently in different mediums?
Due to different densities the way will slow down or speed up
What happens when a wave enters a more dense medium?
The wave slows down and bends towards the normal
What happens when a wave enters a less dense medium?
The wave speeds up and bends away from the normal
What happens to wavelength and frequency during refraction.
Wave speed changes and therefore wavelength or frequency must change
Frequency never changes so wavelength must always change
What is dispersion?
Dispersion is when white light spreads out into 7 different colours - a rainbow
This is because he different wavelength inside of visible light refract by different amounts
What is refractive index?
The ratio of the speed of a wave in two different regions
What is the refractive index of a vacuum?
1
What is the equation for refractive index?
Refractive index = speed of light in vacuum / speed of light in material
What is snells law?
It links the equation for refractive index to the angle of incidence and refraction
What is snells equation?
Refractive index = sin(i) / sin(r)
What is total internal reflection?
When no refraction occurs and the light is reflected back into the denser medium
What are the two criteria for total internal reflection?
The rays of light must be going from a more dense to a less dense medium
The angle of incidence must be greater than the critical angle
What is the critical angle?
The angle of incidence when the ray refracts at a 90 degree angle
What id the formula for a critical angle?
SinC = 1/n. Or. Sin critical angle = 1 / refractive index
How do converging lenses work?
Convex lenses that refract the light inwards to a single point
How do diverging lenses work?
In concave lenses the light is refracted outwards and is dispersed
Explain where the principal focus will form.
On convex lenses - where the rays meet
On concave lenses - where the rays image meet behind lens
There is a principal focus on both sides, equal distance from the middle