Physics 1 Flashcards
(40 cards)
What do waves transfer?
They do this without transferring what?
Transfer energy without transferring matter
What do all electromagnetic waves have in common?
They all travel at the same speed through a vacuum – the speed of light (300’000’000m/s)
Name the electromagnetic spectrum from shortest to longest wavelength
Gamma (shortest) X-rays Ultra-violet Visible light Infra red Microwaves Radio waves (longest)
What is a longitudinal wave and what does it look like?
Vibrations in the same direction as the wave (e.g. sound)
What can happen when radiation is absorbed by a substance?
Radiation may make things hotter, or set up an alternating current with the same frequency as the radiation itself
What are the effects of these types of electromagnetic radiation on living cells: -
a) Radio waves & visible light
b) Microwaves & infrared
c) X-rays, UV and gamma rays
Radio waves & visible light have very little effect on cells
Microwaves and infrared can cause heating of cells
X-rays, UV and gamma rays can cause ionization of cells and lead to mutations, cancers and death
How can the harmful effects of X-rays be reduced
Reducing exposure & using lead aprons
How can the harmful effects of UV radiation be reduced?
Reduce exposure to the Sun (using a broad spectrum sun screen)
How are these electromagnetic waves used: -
a) Radio waves
b) Microwaves
Radio waves: communications
Microwaves: heating food & sending information (e.g. mobile phones)
How are these electromagnetic waves used: -
a) Infrared
b) Visible light
Infrared: communications (phone & via optical fibres), remote controls and electric heaters
Visible light: used to send information via optical fibres
How are these electromagnetic waves used: -
a) Ultra-violet
b) X-rays
UV: security tags and sun-beds
X-rays: imaging the body (broken bones)
How are gamma rays used?
Sterilising surgical equipment by killing bacteria & radiotherapy for cancer patients
Which 4 forms of electromagnetic radiation can be used for communications?
Communications via: radio waves, microwaves, infrared waves (optical fibres) and visible light (optical fibres)
Why are microwaves used to communicate with satellites?
Microwaves are able to pass through the Earth’s atmosphere to reach the distant satellites
What is a transverse wave and what does it look like?
Vibrations which are sideways (e.g. light
What are rarefactions and compressions?
Regions where the wave is pulled apart (rarefactions) and pushed together (compressions)
What is the formula for calculating the speed of a wave (triangle will also help)
Speed (m/s) = Frequency (Hz) x Wavelength (m)
What properties effect waves?
Waves can be reflected, refracted and diffracted
How can light be reflected?
Light can reflect off an even surface (clear) or from an uneven surface (diffuse)
What is refraction?
Refraction occurs as light can bend at the boundary between materials of different densities
What is the link between the angle of incidence and an angle of reflection
Angle of incidence = angle of reflection
How can the refractive index be worked out?
Refractive index = sin i ÷ sin r
What is constructive interference?
Where two waves arrive in step reinforcing one another (increasing the amplitude)
What happens if the size of a gap is made similar to the wavelength of a wave?
diffraction increases
