waves pt2 Flashcards
what type of wave is an electromagnetic wave
an electromagnetic wave is a transverse wave
what do all electromagnetic waves have in common
all electromagnetic waves travel at the same velocity in air or in a vacuum
describe the electromagnetic spectrum
the electromagnetic spectrum extends from low frequency, low energy waves to high frequency, high energy waves
can human eyes detect electromagnetic waves
human eyes are only capable of detecting visible light
what does the wavelength of an electromagnetic effect
the wavelength of an electromagnetic wave affects how it is absorbed, transmitted reflected, or refracted by different substances. this affects its uses.
what does the direction of refraction depend on
the angle at which the wave hits the boundary
the material
what’s it called when a material affects refraction
for light rays, the way in which a material effects refraction is called its refractive index
describe how light travels from a material
from a material with a low refractive index to one with a higher refractive index, it refracts towards the normal
from a material with a high refractive index to one with a lower refractive index, it bends away from the normal
why does refraction happen
refraction is due to the difference in the wave speed in the different media
what happens when a light wave enters at an angle
when a light wave enters at an angle, a medium in which it travels slower
the first part of the light wave to enter the medium slows down.
the rest of the wave continues at higher speeds
this causes the wave to change direction, towards the normal
how can waves be refracted?
when waves reach a boundary between one medium and another, they can be refracted
what happens when constructing ray diagrams
rays must be drawn with a ruler
each straight section of ray should have a single arrow drawn on it to indicate the direction of movement
where the rays meets the boundary should be drawn at right angles to the boundary
all relevant angles should be labled
why are ray diagrams used
ray diagrams are used whenever a diagram is needed to represent how light moves from one place to another
name some examples of electromagnetic waves
radio waves microwaves infrared uv lights visible light x rays gamma rays
what are radio waves used for and describe them
radio waves are used for televisions, radio, Bluetooth
radio waves are low energy waves and therefore, not harmful, making them ideal for radio transmission
what are microwaves used for and describe them
microwaves are used for satellites, communications, cooking food
microwaves travel in straight lines through the atmosphere. this makes them ideal for transmitting signals to satellites in orbit and transmitting them back down to recievers
what are infrared waves used for and describe them
infrared waves are used ofr electrical heaters, cooking food, infrared camares
what is visible light used for and describe them
visible light waves are used for fiber optic communications
visible light travels down optic fibres from one end to the other without being lost through the sides
what are ultraviolet waves used for and describe them
ultraviolet waves are used for energy effiecient light bulbs, security marking, sunbed
n energy-efficient light bulbs, UV waves are produced by the gas in the bulb when it is excited by the electrical current these UV waves are absorbed by the coating on the bulb, which fluoresces giving off visible light
what are x rays used for and describe them
x rays are used for medical imaging and treatments
x rays are able to penetrate soft tissue but not bone a photographic plate behind a person will show a shadow of where the bones are
what are gamma rays used for and describe them
gamma rays are used for sterilizing food, treatment of tumors
gamma rays are the most energetic of all electromagnetic waves and can be used to destroy bacteria and tumor
what can radio signals be caused by
radio signals can be cause by oscillations in electrical circuits i.e an alternating current
what is the frequency of the radio wave
the frequency of the radio wave produced matches the frequency of the electrical oscillation. this is how a radio signal is produced
how is the signal received?
when radio waves are absorbed by a conductor they may create an alternating current with the same frequency as the radio wave. this is how the signal is received
what happens when oscillation is induced
when oscillation is induced in an electrical circuit it creates an electrical signal that matches the wave
how can EM waves be generated?
changes in atoms and the nuclei of atoms can result in EM waves being generated or absorbed over a wide frequency range
what are the other ways waves can be generated?
electrons moving between energy levels as a result of heat or electrical excitation can generate waves
changes in the nucleus of an atom can generate waves i.e. an unstable nucleus can give out excess energy as gamma rays
which waves are dangerous for the body
ultraviolet waves, x rays and gamma rays carry enough energy to have hazerdous effect on the human body
what are those dangers?
ultraviolet waves can cause the skin to age prematurely and increase the risk of skin cancer
