6.2 electromagnetic waves Flashcards
What type of spectrum do
electromagnetic waves form?
A continuous 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
In which direction (relative to the normal) do waves refract when entering a denser
medium?
● They bend towards the normal
● The angle of refraction is less than the
angle of incidence
What type of waves can be produced by
oscillations in an electrical circuit?
radio waves
How can radio waves create an
alternating current in a circuit?
When radio waves are absorbed, they
can induce oscillations in a circuit with
the same frequency as the waves
themselves.
Where do gamma rays originate from?
They originate from changes in the
nuclei of atoms.
What health effects can ultraviolet waves cause?
● They can cause the skin to age
prematurely
● The can increase the risk of
developing skin cancer
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
Give three practical uses for infrared
radiation
- Electrical heaters
- Cooking food
- Infrared cameras
Give two practical uses for microwave
radiation.
- Satellite communications
- Cooking food
Give two practical uses for radio waves.
- Television transmission
- Radio transmission
What wave phenomenon is used by
lenses to form an image?
refraction
How does a convex lens form an image?
Parallel rays of light are refracted and
brought together at the
principal focus.
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
Why does magnification not have a unit?
● It is the ratio between image height
and object height
● Ratios do not require units
What determines the colour of visible
light waves?
The wavelength and frequency of the
light waves.
What colour of visible light has the
highest frequency?
blue
What colour of visible light has the
largest wavelength?
red
What is meant by the term ‘specular
reflection’?
Reflection from a smooth surface in a
single direction.
What is meant by the term ‘diffuse
reflection’?
Reflection from a rough surface which
causes scattering.
How does a red colour filter work?
● A red filter absorbs all wavelengths of
light other than those in the red range
of the spectrum
● This means only red light passes
through the filter
What determines the colour of an
opaque object?
● Different objects reflect different
wavelengths of light by different
amounts
● The wavelengths that are most
strongly reflected determine the colour
What happens to the wavelengths of
light that aren’t reflected by an opaque
object?
Any wavelengths that aren’t reflected are
absorbed by the object
What colour does an object appear if all
wavelengths are reflected by equal
amounts?
white
What colour does an object appear if all
wavelengths are absorbed?
black
