EM waves Flashcards
What type of waves are EM waves?
transverse - light is an example of an EM wave
Where do EM waves transfer energy to and from?
the source of the wave to an absorber
Hot objects transfer energy emitting infrared radiation
this radiation is absorbed by the surrounding air
All Em waves travel at the same velocity thru air or a a vacuum.
Visible light is the only part of the EM spectrum that can be detected by the naked eye.
Each colour of light has a different wavelength and frequency. Order:
long wavelength + lower frequency to shorter wavelength + shorter frequency.
Red, orange, yellow, green, blue, indigo, violet
What is the order of Em waves from long wavelength + lower frequency to shorter wavelength + shorter frequency?
Radio waves , micro waves, infrared waves, visible light, ultraviolet waves, X-rays, gamma rays.
EM waves form a continuous spectrum over a range of frequencies.
So the cut off between one wave and another isn’t always clear
Do EM waves need a medium to travel thru?
NO
What is the speed that EM waves travel through in a vacuum?
3 x 10^8 m/s
(the speed of light)
How do EM waves interact with diff materials?
Different EM waves interact differently with different materials
Large range of frequencies coz EM waves are generated by a variety of changes in atoms and their nuclei - What does this explain?
why atoms can absorb a range of frequencies - each one causes a different change.
What can be said as the frequency increases along the spectrum?
the energy of the waves increase with an increased frequency
Why do different materials interact differently with different wavelengths of waves?
Substances will absorb, transmit, refract or reflect electromagnet waves in ways that vary with wavelength
Different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with wavelength .
Some effects, for example refraction, are due to the difference in velocity of the waves in different substances.
When light enters a denser medium it slows down, what does this mean for shorter wavelengths?
shorter wavelengths slow down more than longer wavelengths
Why does dispersion occur of white light in a prism?
The different wave lengths refract a different amount, and therefore spread out creating a rainbow effect. When refracting, the speed decreases and wavelength decreases too in denser material, the horizontal lines show the “wave-fronts” of the waves (imagine each line is each maxima of the transverse wave)
What are risks of UV radiation?
Sunburn, blindness, premature ageing of the skin, and increased risk of skin cancer.
How can we prevent UV damage?
Sun cream
What does it mean when electrons have moved to a higher orbit?
they’ve absorbed EM radiation.
What does it mean when electrons fall to a lower orbit?
They’ve emitted EM radiation.
If an electron gains enough energy, it can leave the atom to form an ion….
So gamma rays originate from changes in the nucleus of an atom.
How do we prevent damage from X-rays and gamma rays?
minimal exposure to them (the high frequency/energy waves)
Ultraviolet waves, X-rays and gamma rays can have hazardous effects on human body tissue…
The effects depend on the type of radiation and the size of the dose.
What is the radiation dose?
Radiation dose is a measure of the risk of harm resulting from an exposure of the body to the radiation.
What is the radiation does measured in?
in Sieverts (Sv)
1000 millisieverts (mSv) = ?
= 1 sievert (Sv)
What is the yearly radiation does for the body of a worker? (the limit)
20 mSv
