Waves (11) Flashcards
What are the 2 types of wave
Longitudinal
Transverse
A longitudinal wave is where the direction of the wave is ____________ to the direction of particles vibration
Parallel
Example of a longitudinal wave
Sound wave
A transverse wave is where the direction of the wave is ________________ to the direction of particles vibration
Perpendicular
Example of a transverse wave
Light waves, microwaves, x rays, radio waves
What is the amplitude
The height of a wave from its mean position/undisturbed position
What is the wavelength
The distance between successive crests or troughs
What is the frequency
The amount of waves passing a point in 1 second
Unit of amplitude
Meters
Unit of wavelength
Meters
Unit of frequency
Hertz
What is the time period
The time taken by a wave in crossing a certain point
Equation for wave speed:
Wave speed = Frequency x wavelength
1Kilohertz = _________ hertz
1000
All waves transfer energy and information without transferring ___________
Matter
What is diffraction
When a wave bends round edges or through gaps
Diffraction causes waves to ________ round an object
Bend
What does the amount of diffraction depend on
The size of the gap relative to the wavelength of the wave
The narrower the gap or longer the wavelength, the ________ the wave spreads out
More
What are the 7 types of electromagnetic (EM) wave
Radio waves
Micro-waves
Infra-red
Visible light
Ultra-violet
X-rays
Gamma rays
The different colours of visible light depend on the wavelength - red has the ____________ wavelength and violet has the ______________ wavelength
Longest
Shortest
Time period equation:
T = 1/f
Frequency equation:
F = 1/T
How long is one wavelength
From the middle to 1 peak and 1 trough and back to the start
What is the audible range of sound for a human
20-20000Hz
If frequency is greater than 20000Hz then it is known as _________________
Ultrasound
A louder sound has a ______________ amplitude
Higher
A quieter sound has a _____________ amplitude
Lower
A higher pitch has a __________ frequency
Higher
A lower pitch has a __________ frequency
Lower
What is the speed of sound
340m/s
The maximum disturbance caused by a wave is called its _______________
Amplitude
What are the 2 laws of reflection
1) Angle of incidence = angle of reflection
2) Incident ray, reflected and normal are in the same plane
What is refraction
The bending of light as it travels from one optical medium to another
How do you find the refractive index
Sin i / Sin r
How to find the angle of refraction
Angle of refraction = angle of index / refractive index Sin r = Sin i / R.I Once you have found Sin r you must do Sin-1 (sin r) E.g if I = 46 and R.I = 1.45 Then do Sin I and then divide that by 1.45 You will get 0.5 which is Sin r But you just want r so you do Sin−1(0.5) And you will find just r on its own which is 30
Conditions for Total Internal Reflection
Ray of light should travel from more dense material to less dense material.
Angle of incidence should be greater than the critical angle
What is the critical angle
The angle of incidence at which the angle of refraction becomes 90 degrees and light starts to bounce back
Refractive index equation in total internal reflection
1 / Sin ic (ic = critical angle)
What is the critical angle (in degrees)
42 degrees
At the critical angle, the angle of refraction is _____ degrees
90 degrees
What does the refractive index tell you
How fast light travels in that material
Light slows down a lot in glass, so the refractive index is _________
High
Describe an experiment to find the refractive index of a glass block
Draw around a rectangular block on a piece of paper and direct a ray of light through it at an angle. Trace the ray entering and the ray leaving the block before removing the block and drawing in the refracted block. Then, draw in the normal at 90 degrees to the edge of the block at the point where the ray enters the block. Then measure the angle of incidence and the angle of refraction. Then calculate the R.I using Snell’s law R.I = Sin i / Sin r. Done.
How do you use Snell’s law to find critical angles
Sin C (critical angle) = 1 / R.I
The higher the R.I the _____________ the critical angle
Lower
What do optical fibres use
Total internal reflection
How is sound sent by phones
It is turned into electrical energy and back into sound energy
What are the 2 types of electromagnetic signals
Analogue
Digital
____________ signals vary whereas ___________ signals are either on or off
Analogue
Digital
When you amplify an ______________ signal, the noise is amplified too - so every time it’s amplified, the signal loses quality. However with a ___________ signal, the noise is just ignored, so the signal remains high quality
Analogue
Digital
If analogue waves are of a similar frequency, it can cause ________________
Interference
Name a machine that can display sound waves
An oscilloscope
What do we mean by a ‘normal’ line
The line perpendicular or at 90° to the mirror
When is light refracted away from the normal line?
As it is leaving the glass into the air
Why is a wave refracted?
The speed of the wave changes
What do we get at low angles of incidence (i)
Refraction
At the critical angle light does what?
Travels across the edge
What happens if angle i is above the critical angle
Total Internal Reflection
The critical angle is the angle at which ________ starts
Total internal reflection
As light is entering a glass block. It comes in at the ____ angle as it comes out
Same
Give 2 examples of what are optical fibres used for
Telecommunications
Endoscopes in medicine
State a benefit of optical fibres
Very fast signals
What is the difference between convex and concave
Concave, ) (
Convex ( )
Concave bends the light further apart
White light consists of ___ colours
All colours
What is the order of the electromagnetic spectrum
Radiowaves
Microwaves
Infrared
Visible light
Ultraviolet rays
X-rays
Gamma rays
Does frequency increase as you go up or down the electromagnetic spectrum
Frequency increases as you go down the spectrum so gamma has the highest frequency
Does wavelength increase as you go up or down the electromagnetic spectrum
Wavelength increases as you go up the spectrum so radiowaves have the highest wavelength
Does energy increase as you go up or down the electromagnetic spectrum
Energy increases as you go down the spectrum so gamma has the highest energy
Give one use of radiowaves
Communication
Give one use of microwaves
Cooking
Communication
Give one use of infrared
Remote controls
Security systems
Night vision
Give one use of visible light
Vision
Photography
Give one use of ultraviolet rays
Sun beds
Give one use of x-rays
X-rays (observing the internal structure of objects)
Give one use of Gamma rays
Sterilisation of food and equipment treating cancer
Dangers of radiowaves (due to over exposure)
Nothing
Dangers of microwaves (due to over exposure)
Internal heating of body tissue
Dangers of infrared (due to over exposure)
Skin burns
Dangers of visible light (due to over exposure)
Damage eyes
Dangers of ultraviolet (due to over exposure)
Damage to skin + eyes including cancer
Dangers of x rays (due to over exposure)
Damage to cells leading to burns and cancer
Dangers of gamma rays (due to over exposure)
Damage to cells leading to burns and cancer
