Waves Flashcards
What are the 2 types of waves?
Transverse and longitudinal
What are transverse waves?
Vibrations are perpendicular to the direction of energy transfer
All EM waves, eg visible light, radio waves, microwaves
Looks like a slinky moved up and down
What are longitudinal waves?
Vibrations are the same direction as energy transfer
Eg sound waves, seismic waves
Looks like a slinky when you push the end
Equation to calculate wave speed
wave speed = frequency x wavelength
v = f x l
Equation to calculate frequency
frequency = 1 / time period f = 1 / T
What is the amplitude?
The height of a wave
What is the frequency?
How many waves there are passing a certain point per second
What is the wavefront?
An imaginary surface used to represent the vibrating part of a wave
What is the wavelength?
The distance from one wave peak to the next
What is the (time) period?
The time it takes for one complete wave to pass a certain point
What is the Doppler Effect?
When the object is moving towards an observer, the waves are shifted to a higher frequency and the wavelength becomes shorter.
What is the order of the EM spectrum?
from long wavelength/low frequency to short wavelength/high frequency
Radio waves Microwaves Infrared Visible light Ultraviolet X rays Gamma rays
What are radio waves used for?
Broadcasting and communications
What are microwaves used for?
Cooking and satellite transmissions
What is infrared used for?
Heaters and night vision equipment
What is ultraviolet used for?
Fluorescent lamps
What are x rays used for?
Observing the internal structure of objects and materials, eg broken bones
What are gamma rays used for?
Sterilising food and medical equipment
What effect does excessive exposure to microwaves have?
How can you prevent this?
Internal heating of body tissue
Microwave ovens should have shielding to protect the user.
What effect does excessive exposure to infra-red have?
How can you prevent this?
Skin burns
Don’t touch hot objects
What effect does excessive exposure to ultraviolet have?
How can you prevent this?
Damage to skim cells and blindness
Wear sunglasses, sun cream, wide brim hat
What effect does excessive exposure to gamma rays have?
How can you prevent this?
Cancer, mutation
Radioactive sources should be stored in lead-lined boxes
What is the speed of light?
3 x 10^8 m/s
Are light waves transverse o longitudinal?
Transverse
What is the law of reflection?
Angle of incidence = angle of reflection
i = r
What is the refractive index of a material?
Tells you how fast light travels through it
Equation to calculate refractive index
n = sin i / sin r
When the angle of incidence is less than the critical angle:
i is less than the angle of refraction
Most of the light passes out
When the angle of incidence is the critical angle:
The angle of refraction is 90°
The refracted ray comes out along the surface
When the angle of incidence is greater than the critical angle:
All light is totally internally reflected (TIR)
Law of reflection is observed
What is the relationship between the critical angle angle and the refractive index?
sin C = 1 / n
What type of waves are sound waves?
Longitudinal waves, can be reflected and refracted
What is the frequency range for normal human hearing?
20Hz - 20,000Hz
