Electromagnetic Waves Flashcards
(1) X- rays are … waves with… frequency
Electromagnetic waves with very high frequency
(2) Some users believed that sunglasses would protect their eyes from the X-rays.
Explain how effective this would be as a precaution.
very little effect / not
effective (1)
• X-rays can easily
penetrate sunglasses (1)
(1) The device shown in the picture was invented not long after the discovery of
X-rays.
It emitted X-rays through the window
Many people who had used it for a long time had become seriously ill.
State one of the effects this machine may have had on them.
cancer damage to cells damage to DNA damage to tissue damage to bones damage to skin damage to organs killing cells mutation mutating cells marks on skin sterilisation infertility re-arrangement of cell structure radiation poisoning
(2) The device shown in the picture was invented not long after the discovery of
X-rays.
It emitted X-rays through the window
The device was advertised as ‘harmless’.
Suggest why people used this device for many years.
took a long time for effects to become apparent (1) • it was new /scientific (1) • risks not properly understood (1) • it removed hair successfully (1)
(6) ) There is a hair removal device which is currently available in some specialist clinics.
It uses a low energy infrared laser beam. The makers say that this is much less
dangerous than the X-ray device.
By considering the dangers associated with both devices, discuss whether the
infrared laser device should be put on general sale to the public.
infrared frequency much lower than X-rays
• X-rays very penetrating
• X-rays potentially more dangerous to the operator
• infrared can cause skin burns
• laser is very concentrated
• specialised clinics are controlled environments
• safe operation depends on training
• our knowledge of EM radiation is still not complete
The discussion makes some of the following links
• lower frequency of infrared makes it potentially less dangerous
than X-rays
• high penetration of X-rays makes it difficult provide adequate
shielding
• the concentration of energy by the infrared laser makes it
more dangerous than otherwise
• controlled environment of a clinic provides better safety and
more thorough training
• difficulty of ensuring proper maintenance /correct dosage if
used domestically
• lack of knowledge could mean there are long term effects still
not known
The discussion makes some of the following conclusions
• easier shielding of infrared compared to X-rays means there is
less risk to operators and /or patient
• difficulty of ensuring proper control means it is not suitable for
domestic use
• lack of full understanding of long term effects means it is
better to err on side of caution
(1) Suggest why radio telescopes do not have to be placed high up a mountain.
radio waves are not absorbed by
the atmosphere
(2) One theory of the origin of the Universe predicted that there should be
cosmic background radiation with a wavelength of about 1 mm.
Explain why scientists had to wait until the development of space flight
before they could study this radiation in detail.
1 mm waves are in the microwave region (1)
• which is (completely)
absorbed by atmosphere
(1)
• space flight enabled
telescopes to be put above
atmosphere /in space (1)
(2) ) The electromagnetic radiation from most galaxies has a red-shift.
Suggest why, when a galaxy has a very large red-shift, some of its visible light
is not detected through the Earth’s atmosphere.
light might be shifted into infrared region (1) • (some) infrared is (strongly) absorbed by atmosphere (1)
(1) All electromagnetic waves are… in a vacuum
transverse and have the same speed in a vacuum
(1) All electromagnetic waves have both uses and dangers.
Their potential danger increases when
frequency increases and wavelength decreases
(2) Explain why using a television remote control does not burn anyone.
- wavelength / frequency (1)
* are different (1)
(3) Gamma rays can cause cancer.
Gamma rays can also be used to treat cancer.
Explain how gamma rays can do both.
gammas change cell growth / eq (1) • (so can) cause uncontrolled growth (1) • (but also can) be focussed to (kill cancer cells)(1) • without damaging other cells
(1) Which row of the table is correct for both infrasound radiation and infrared
radiation?
longitudinal, transverse
(1) State the amplitude of this sound wave.
5 (cm)
(1) X-rays
visible light
infrared
Arrange these three waves in order of decreasing
wavelength.
longest wavelength -> shortest wavelength
infrared , visible light , X-rays
(1) Which parts of the electromagnetic spectrum are used for both
communication and cooking?
infrared and microwaves
(1) Visible light has a
lower frequency than ultraviolet
(2) Describe a harmful effect of ultraviolet radiation
UV penetrates the skin / can damage normal cells/ cause cell mutation/ionise cells (1) • can cause (skin) cancer / can cause premature ageing (1)
(2) Explain why ultraviolet radiation is likely to be more dangerous to humans
than infrared radiation.
(ultraviolet/it) has a higher frequency (than infrared) (1) • (therefore ultraviolet/it) has higher (photon) energy (1) • (ultraviolet/it) penetrates further /(ultraviolet/it) causes ionisation (1)
(6) Herschel discovered invisible rays beyond one end of the visible spectrum.
Ritter discovered invisible rays beyond the other end of the visible spectrum.
Compare and contrast the two experiments leading to these discoveries.
You may draw labelled diagrams to help with your answer.
Similarities
• used white light from the Sun
• glass prism
• produced a visible spectrum
(Herschel’s) infrared experiment
• used a thermometer to measure the temperature of different
colours of the visible spectrum
• temperature increased towards the red end
• temperature increased more past the red end of the
spectrum.
• temperature rise was due to invisible rays named infrared
(Ritter’s) ultraviolet experiment
• used silver chloride on paper this slowly turns black in visible
light.
• silver chloride turned black faster as the paper was put at
the violet end of the spectrum
• beyond the violet the silver chloride turned black even more
rapidly
• due to the presence of invisible rays (originally called
chemical rays) now called ultraviolet
(2) X-rays from a star travel to a space telescope in orbit around the Earth.
Explain why visible light from the same star takes the same time to reach the
telescope.
(all e-m waves) have same
speed (1)
• in {space/vacuum} (1)
(1) Which of these ionising radiations is from a radioactive source and is also part of
the electromagnetic spectrum?
gamma rays
(2) An X-ray of wavelength 2.0 nm has a frequency of 1.5 1017 Hz.
1.0 nm = 1.0 10–9 m
Calculate the speed of the wave.
substitution ie (v =) 1.5 x 1017 x 2 x 10-9 (1) evaluation ie (v =) 3 x 108 m/s (1)
(2) Explain why ultrasound rather than X-rays are used for foetal scanning.
{X- rays are / ultrasound
is not} dangerous (1)
• (because X-rays) can
{damage / harm} {tissue
/ DNA} OR
mutate cells
OR
reverse argument for
ultrasound (1)(1) Name one type of radiation that can reach the surface of the Earth from stars.
radio
• visible
• microwave
(1) Name one type of radiation from stars that cannot be detected at the Earth’s
surface but can be detected using satellites.
X-ray
• gamma ray
• far infrared
