1) Waves Flashcards
Define transverse waves
Particles vibrate perpendicularly to the direction of energy transfer
Define longitudinal waves
Particles vibrate parallel to the direction of energy transfer
What is the wavelength?
distance between two peaks
What is the amplitude?
distance from peak to the middle
What is the symbol for wavelength?
Greek letter pronounced lambda [ λ ]
What is frequency measured in?
Hertz (Hz)
What does a frequency of 1 Hz mean?
1 wave per second
What is the time period of a wave?
The time taken to produce one wave
What is the equation linking time period (T) and frequency (f)?
T = 1/f
What is the equation relating wave speed (v), frequency (Hz) and wavelength (lambda)?
“wave speed = frequency bywavelength”
What is wavespeed measured in?
m/s
What is wavelength measured in?
metres
What are the uses of radio waves?
- broadcasting
- communications
What are the uses of microwaves?
- cooking
- satellite transmissions
What are the uses of infrared?
- heaters
- night vision equipment
What are the uses of visible light?
- optical fibres
- photography
What are the uses of ultraviolet?
- fluorescent lamps
What are the uses of x-rays?
- observing the internal structures of objects and materials, including for medical applications
What are the uses of gamma rays?
- sterilising food
- medical equipment
What type of waves has the longest wavelength and lowest frequency?
Radio waves
What type of waves have the shortest wavelength and highest frequency?
Gamma rays
List the 7 types of radiation in the electromagnetic spectrum in order of lowest frequecy and longest wavelength to highest frequency and shortest wavelength
- radio waves
- microwaves
- infra-red
- visible light
- ultra violet
- X-rays
- gamme rays
What effects on the body do microwaves have?
- internal heating of body tissue
What effects on the body does infrared have?
- skin burns
What effects on the body do radiowaves have?
- none
What effects on the body does visible light have?
- blindness
What effects on the body does ultra violet have?
- damage to surface cells
- cancer
- blindness
What effects on the body do gamma rays have?
- cancer
- DNA mutations
Define Doppler effect
“The change in wave frequency during the relative motion between a wave source and its observer”
How long are the wavelengths when the sound is travelling towards the observer?
- short
- high frequency
- high pitched sound
How long are the wavelengths when the sound is travelling away from the observer?
- longer wavelength
- lower frequency
- lower pitch
Define incident ray
The ray of light that is going towards the normal
Define reflection ray
The ray that is going away from the normal
What is the law of reflection?
- That i=r
- angle of incidence = angle of reflection
What degree is the normal to the mirror/glass block?
90° or perpendicular
Define critical angle
The angle where light will be refracted along the surface of the material
What is the critical angle of glass?
42°
Define total internal reflection
When the angle of incidence is greater that the critical angle, all the light is reflected
What happens in an optical fibre?
The light travels down the fibre by repeated total internal reflection
Define refraction
Refraction is the change in direction of light as it enters either a more or less dense medium and either slows down or accelerates.
What is the name given to a medium which light travels slower?
Optically dense
What happens when light enters a more optically dense material?
The light refracts towards the normal
What happens when light enters a less optically dense material?
The light refracts away from the normal
Define refractive index (n)
The ratio of the speed of light in a material to the speed of light in a differently dense material
How do you find the refractive index?
n = sin i (angle of incidence)/ sin r (angle of refraction)
Rearrange the refractive index equation to find i (angle of incidence)
i = sin-1(n sin r)
Rearrange the refractive index equation to find r (angle of refraction)
r = sin-1(sin i/n)
What is the equation linking critical angle (c) and the refractive index (n)?
sin c = 1/n
Can sound travel through a vacuum?
no
Are sound waves transverse or longitudinal waves?
Longitudinal
