Level 1 Physical Science: Waves & Light Flashcards
What is a wave
A transfer of energy from one point to another without the transference of matter. Some need a medium to travel others can travel through a vacuum.
What are the 2 types of waves
Transverse and Longitudinal
What is a transverse wave
Particles oscillate at 90° to the direction of the wave.
How do you remember to draw a transverse wave
s,s ~
Examples of transverse waves
Water waves, light, earthquake (surface wave)
What is a longitudinal wave
Particles oscillate parallel to the direction of the wave.
What are the two parts of a longitudinal wave
Compression & rarefaction
Examples of longitudinal wave
Sound, earthquake (propagation wave)
What is a light wave
Transverse, can travel through a vacuum.
What is a sound wave
Longitudinal, needs a medium to travel through, caused by a vibrating object e.g a speaker.
What type of wave is a light wave
Transverse
What type of wave is a sound wave
Longitudinal
What are the 3 formulas to do with waves
T=1/f V=d/t V=fλ
What is the formula for period or frequency
T=1/f
What is the formula for the speed/time/distance of the wave/wave has travelled
V=d/t
What is the formula for the wavelength/speed/frequency
V=fλ
What are 4 properties of a wave
Wavelength, Frequency, Amplitude, Period
What is the definition of Wavelength
Distance from one point of the wave to the next equivalent point e.g crest→crest
What is the definition of Frequency
Number of waves that pass a point in a second.
What is the definition of Amplitude
The maximum displacement from the equilibrium position.
What is the definition of Period
Time for one complete oscillation/wave to pass a point.
What is the symbol of Wavelength
λ
What is the symbol of Frequency
f
What is the symbol of Amplitude
A
What is the symbol Period
T
What is the unit for Wavelength
m
What is the unit for Frequency
Hz
What is the unit for Amplitude
m
What is the unit for Period
s
What is the definition, symbol & unit for Wavelength
Distance from one point of the wave to the next equivalent point e.g crest→crest. Symbol λ, unit m
What is the definition, symbol & unit for Frequency
Number of waves that pass a point in a second. Symbol f, unit Hz
What is the definition, symbol & unit for Amplitude
The maximum displacement from the equilibrium position. Symbol A, unit m
What is the definition, symbol & unit for Period
Time for one complete oscillation/wave to pass a point. Symbol T, unit s
The higher the frequency the _________ the wavelength
shorter
The lower the frequency the ________ the wavelength
longer
The shorter the wavelength the _________ the frequency
higher
The longer the wavelength the ___________ the frequency
lower
What is the smooth reflection of light
Even reflection of light reflection is regular
What is the rough reflection of light
Irregular reflection or diffuse.
What is the incident ray (plane mirror)
The ray that collides with a mirror.
What is the reflected ray (plane mirror)
The ray that ‘bounces off’
What is the normal (plane mirror)
Drawn at 90° to the surface
What is the rule for a plane mirror
θi=θr (angle of incidence=angle of reflection)
What happens to an image in a plane mirror
Image is:
Same size, appears same distance from mirror, virtual, laterally inverted.
What is refraction of light
Happens when light travels from one medium to another, it will either speed up or slow down.
The higher the optical density the slower it travels.
When light passes from a less to more optically dense medium it slows down and refracts towards the normal.
What happens to the light ray when it goes from a higher optically dense medium to a lower optically dense medium.
The light ray will speed up and bend away from the normal
What happens to the light ray when it goes from a lower optically dense medium to a higher optically dense medium.
The light ray will slow down and bend towards the normal.
What colour light ray has the shortest wavelength
Violet
What colour light ray has the highest frequency
Violet
What colour light ray travels slowest in a prism
Violet
What colour light ray diffracts the most in a prism
Violet
What colour light ray has the longest wavelength
Red
What colour light ray has the lowest frequency
Red
What colour light ray travels fastest in a prism
Red
What colour light ray diffracts the least
Red
What is the visible light spectrum
ROYGBIV
What is the critical angle
When Light travels from a medium to a less dense medium, a certain θi will produce a θrefraction of 90°. This θi is the critical angle for this material. If angle of incidence is greater than the critical angle total internal reflection occurs.
What wavelength diffracts more
A longer wavelength
What wavelength diffracts less
A shorter wavelength
What is diffraction
If a travelling wave comes across a barrier (e.g a rock, wall, hill) the wave will continue to bend around the edge of the barrier.
The amount of diffraction that happens depends on the wavelength of the wave.
What is the definition of diffraction
The bending of a wave around the edge of a barrier is called diffraction.
The _____ the wavelength the further it diffracts around the barrier.
longer
What is light
Light is a type of electromagnetic radiation. Electromagnetic radiation occurs as waves and includes:
Visible light, X-rays, Microwaves, Radiowaves
What is reflection
If a wave strikes a surface it is reflected, smooth surfaces reflect light evenly (e.g a mirror, calm lake). We call these regular reflectors. Rough surfaces reflect unevenly and give a blurred image (e.g crumpled tin foil, a lake in the wind). We call these diffuse reflectors.
What are the 2 rays that come from a mirror when light is reflected into it?
The incoming wave is called the incident ray
The wave that comes off the mirror is called the reflected ray.
What is the important law about angle of incidence and angle of reflection.
The law of reflection states that the angle of incidence= angle of reflection (θi=θr)
When is a real image formed
A real image is formed when real rays converge (meet).
What is a virtual image
A virtual image is the image that appears to be formed behind a mirror.
What are the qualities of a virtual image
A virtual image can only be seen in the mirror.
It can not be reformed/reflected onto a screen.
The image is not ‘real’ since no real light rays from the object reach the position of the virtual image.
What is refraction
Refraction is the BENDING of light as it crosses the boundary between two transparent mediums.
What does every transparent medium have?
Every transparent medium has an ‘optical density’ which determines how a light wave changes direction.
The more optically dense something is the _________ light will travel through it.
slower
What changes when light passes through a transparent medium.
The speed, wavelength and direction may change.
What stays the same when light passes through a transparent medium.
The frequency stays the same.
What happens to light when it passes from one medium to another?
The light ray will either ‘bend’ towardes or ‘bend’ away from the normal.
What happens to light when it passes from a less dense medium to a more dense medium
It slows down and refracts (bends) towardes the normal
What happens to light when it passes from a more dense medium to a less dense medium
It speeds up and refracts (bends) away from the normal
What are the 2 criteria required for total internal reflection.
The incident ray must strike the interface at an angle greater than the critical angle
Light must be travelling from a more optically dense medium to a less optically dense medium. (e.g glass→air or water→air
What is dispersion of light
The light given off by the sun, or lightbulbs is called white light. White light is made of a whole range (or spectrum) of colours mixed together., We can see this spectrum if we pass white light through a glass prism. The rainbow of colours is called the visible spectrum and contains the colours red, orange, yellow, green , blue, indigo, violet.
What is the reason white light splits into the colours of the visible spectrum (when shone through a prism on an angle)
Because each colour is refracted at a slightly different amount as it changes mediums. This process is called dispersion.
What is the definition of a wave
A wave is a disturbance that travels through a medium from one location to another
What is a medium
A medium is a substance or material that carries the wave.
What is the function of a wave
The function of a wave is to carry ENERGY from one place to another
The energy from a wave moves from one place to another ______ transferring any _____
without matter
What are the 2 things waves can be
Mechanical and electromagnetic
What is a mechanical wave
These need a substance or medium to travel through e.g water or sound waves
What is a electromagnetic wave
These DO NOT need a medium to travel through. They can also travel through a vacuum.
What is a transverse wave
The waves travels at right angles to the movement of the medium. ‘Trans’ means ‘across’ therefore transverse waves oscillate particles 90° to the direction the waves are travelling.
What is a longitudinal wave
The particles in longitudinal waves vibrate/oscillate parallel to the direction the water is moving.
For a transverse wave what does f=?
For a transverse wave f= The number of crests (or troughs) that pass a point per second.
For a longitudinal wave what does f=?
For a longitudinal wave f= The number of compressions (or rarefaction) that pass a point per second.
What is the equation for frequency?
f=1/T
What is the equation for period?
T=time taken/# of waves
What relationship do period and frequency have?
An inversely proportional relationship.
You can use f=1/T OR T=1/f
Period, T= number of seconds per oscillation
Frequency, f= number of oscillations per second
The ________ the amplitude the louder the sound
higher
What is the speed of a wave
The speed of a wave is constant in any particular medium, but if the wave travels from one medium to another, the speed changes.
What are the 2 formulas for speed?
v=d/t & v=fλ
What is reflection of sound called
Reflection of sound off a hard surface is called an echo.
What is diffraction
If a travelling wave comes across a barrier the wave will continue to bend around the edge of the barrier.
What does the amount of diffraction depend on
The amount of diffraction depends on the wavelength of the wave.
What happens when a wave diffracts?
It stays in the same medium. Therefore the frequency, speed and wavelength do not change.
What are the 3 steps of diffraction in a gap
- Diffraction happens at both edges of a gap, so the wave passing through the gap tends to become more circular in shape.
- The bending of the wave is greatest when the width of the gap is about the same as the wavelength of the wave.
- Less diffraction occurs when the wavelength is smaller than the gap in the barrier.
