6.2 Waves (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
- they 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
- 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 a point known as 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 lens 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
- and ratios do not require units
What symbol is used to represent a convex lens in a ray diagram?
What symbol is used to represent a concave lens in a ray diagram?
What determines the colour of visible light waves?
the wavelength and the 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 that 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
