Unit 4: Week 4 Flashcards
What are EM waves? What is their speed?
Electromagnetic waves are caused by accelerating charged particles through and electric and magnetic fields or by giving them heat energy or through radioactive decay (charged particles produce electric field and accelerating them produces magnetic field) (through space/time) which cause oscillations in those fields- waves. They transfer energy between two different points and are non mechanical transverse waves.
Speed of light 3.00*10^8
How does frequency and wavelength change and what is the effect?
Radio waves end of spectrum has longer wavelength and small frequency meaning it has a low energy E=hf. As you travel towards the gamma end wavelength decreases and frequency increases. This means the it has the energy to ionise (wavelength is small enough to effect sub atomic particles
What is a source of radio waves and what are they used in?
AC into a transmitter. Electrons in the transmitter oscillate at the right frequency to generate radio waves. These are absorbed the metal receiver causing the electrons the oscillate at the same frequency and output a matching AC into the receiver.
Used in communication- tv signals
Same thing with microwaves and phone antenna
What is a source of microwaves and how are they used?
Microwaves are part communication and part heating.
A current (stream of electrons) passes into a magnetron in a microwave.
This makes electrons vibrate at the frequency to give off microwaves. (vibrate more causing heating effect).
Microwaves passes through the food-making water molecules vibrate at the same frequency to give a heating effect.
What is a source of infrared and how is it used?
heating effect- hot objects give out radiant heat which is in the infrared spectrum.
This can be detected by infrared cameras - this can be interpreted by using visable light.
It is used in night vision- colour overlays to make objects clear, search for survivors
among debrie.
What is a source of visible light and what is it used for?
Causes Chemical Charges This is part of the Em spectrum is visible.
Filament in a bulb is a thin wine that current passes through. The filament heats up which causes thermal energy and increase frequency to the point it glows, giving out viable light.
Nuclear fusion in the sun gives off light and infrared energy.
Also used in fiber optic wires in communication (utilises TIR).
The back of the eye/retina absorbs waves win the frequency of viable
light to undergo chemical reactions leading to an electrical signal to the brain in order to interoperate images.
Photosynthesis - chlorophyll absorbs red + blue light to undergo chemical
reactions which produce energy
light produced through chemical reactions is called chemiluminescence
Colour blindness occurs when cones in the back of the
eye have trouble picking up certain frequencies of light.
What is a source of UV and how is it used?
Produces chemical charges/part of UV rays can be ionising.
UV can be produced by passing AC with the correct frequency through
a gas tube to cause transitions in the gas and cause photons with frequencies in the UV spectrum.
This can interact with phosphors coating in florescent tubes causing transitions and producing photons of visible light.
UV (from the Sun) can cause harmful/damage to skin due to it being ionising, the body produces melonIn to increase protection.
UV can make teeth, clothing, fingernails glow due to the presence of
phosphors. (emits viable light in respond to UV).
florecent materials react to UV so can be used as security markers.
What is a source of X-rays and how are they used?
Ionising part of the EMS Hot cathode filament to anode causing transition in tungsten- continuous and characteristic x rays
carry enough energy to cause electrons to excite and leave the atom. The resulting
ions can react easily - Causes damage in living cells
can be used to detect broken bones, screen items without interacting
without them- bags + archeology
What is a source fro gamma radiation and how is it used?
Gamma - Ionisation - Smallest wavelength and highest energy.
Atoms decay to become more stable - a more stable ratio of proton: neutrons
(closer to the stability band). leftover energy is released during/ after radioactive decay.
Due to increased penetration gamma can be used for treatment → Gamma rays at
multiple angles, tracers, sterilise equipment etc
What is the inverse square law
Point sources of gravitational force, electric field, light, sound or radiation obey the inverse square law- as you increase distance the effect decreases by 1/x^2
