6.2 Electromagnetic Waves Flashcards
what type of spectrum do electromagnetic waves form?
a continous spectrum.
order the types of electromagnetic radiation from lowest to highest frequency.
- radio waves
- microwaves
- infrared
- visible light
- ultraviolet
- x-rays
- gamma rays
how do the speeds of EM radiation differ in a vacuum and in air?
electromagnetic waves all travel at the same speed in a vacuum and in air.
what property of waves in different mediums causes refraction?
- velocity
- wave speed is slower in denser materials, causing refraction
what type of waves can be produced by oscillations in an electrical circuit?
radio waves.
in which direction (relative to the normal) do waves refract when enetering a denser medium?
- they bend towards to normal
- the angle of refaction is less than the angle of incidence
where do gamma rays orginate from?
they originate from changes in the nuclei of atoms.
how can radio waves creates an alternating current in a ciruit?
when radio waves are absorbed, they can induce osciallations in a circuit with the same frequency as the wave themselves.
what health effects can X-rays and Gamma rays cause?
- they are ionising radiation so can cause mutations in genes
- they can lead to increased risk of developing various cancers
what health effects can ultraviolet waves cause?
- they can cause the skin to age prematurely
- they can increase the risk of developing skin cancer
what is meant by the focal length of a lens?
the distance from the lens to the principal focus.
what is the difference between the image produced by a convex and a concave lens?
- convex lenses can produce real or virtual images
- concave lenses can only produce virtual images
give three practical uses for infrared radiation.
- electrical heaters
- cooking food
- infrared cameras
give two practical uses for microwave radiation.
- satellite communications
- cooking food
how does a convex lens form an image?
parallel rays of light are refracted and brought together at a point known as the principal focus.
