Electromagnetic Radiation Flashcards
Where in our lives do we use electromagnetic radiation
Broadcasts from tv stations, radio stations and orbiting satellites. Microwave ovens, a remote control to open a garage door, cell phones etc
What are water waves, waves in a string or spring and sound waves called
Mechanical waves
What do mechanical waves require that electromagnetic radiation does not require
A propagation medium
Why doesn’t electromagnetic radiation need a propagation medium
They propagate in an empty space
Why does electromagnetic radiation have a dual nature
It acts a wave and a particle
What is diffraction
The ending or spreading of waves around the edge of a barrier or opening
What is the photoelectric effect
It is an effect that showcases that light, and all electromagnetic radiation has particle properties
What is a photon
A particle of light. It is an energy packet of light
What is the source of electro magnetic radiation
The acceleration of electrical charges. Electric charges in motion cause a change in magnetic field
What is a changed magnetic field always accompanied by
A changed electric field That is perpendicular to the direction of the magnetic field
What are electromagnetic waves
Varying electrical and magnetic fields propagated in the form of waves
What are the seven main groups in the electromagnetic spectrum (in order)
Radio waves, micro waves, infrared, visible light (ROYGBIV), ultra violet, x-rays, gamma rays
What are the properties of electromagnetic waves
- they are transverse waves
- they move the same speed in a vacuum (3 x 10^-8 m.s^-1)
- can move through a vacuum (don’t need a medium to propagate through)
- they can move through mediums but it will move slower than in a vacuum
- transfers energy from one place to another (when charges accelerate they radiate energy)
- they undergo diffraction and interference
What are examples of radio waves
Radio, tv broadcasts, communication
What are the main sources of radio waves
Transmitting antenna as in radio and tv stations
What are the uses of micro waves
- Micro wave ovens (they carry the energy to water molecules in food and heats it)
- radar air control to determine the position of an aircraft
- satellite communication
What is the main source of microwaves
Klystron
What are the uses of infrared waves
- transfers energy or heat and gives us a feeling of warmth in our skins when we stand in front of a heater
- used in thermal cameras
- remote controls
- navigation
What are the main sources infrared
Warm bodies like fires, sun
What are the uses of visible light
- production of food by plants
-to enable us to see things around us
What are the main sources of visible light
Sun, globes
What are the uses of UV rays
-lighting
-optical illumination
- fluorescent pen (highlighter)
-detect forged bank notes
- bees use it because flowers stand out more at this frequency
What are the main sources of UV rays
Sun, florescent lamps
What are the main uses of X-rays
-medical imaging
-CT-scan
- security checks
What are the main sources of X-rays
Discharged tubes
What are the uses of gamma rays
-kills cancer cells
- sterilise food and equipment
- increase shelf life of food
- used to kill bacteria in marshmallows
What is the main source of gamma rays
Radioactive elements
What is the penetrating ability of visible light, UV rays, X rays
Visible light reflects on the human body,
UV rays (from the sun) damaged the skin, x rays are able to penetrate the skin and bone and allow for pictures inside the human body to be taken
What affects the degree of penetration of electromagnetic radiation
The higher the frequency of the electromagnetic radiation the deeper the penetration
What is ionising radiation
Dangerous radiation like UV rays, and x-rays, gamma rays
What protects us from most electromagnetic radiation
The earths atmosphere
What are the two different frequency ranges of UV light
UVA and UVB
What are the negative effects of UVA and UVB
They can damage collagen fibres which result in ageing of skin, DNA damage and possibly skin cancer. Damage to eyes,
How is UV Light used for tanning
The skin produces the brown pigment melanin as a protection against Uv rays.
What makes a good UVB protection sunscreen
A sunscreen with Padimate O, Homosalate, Octisalate, Octinoxate
What makes a good UVA protection sunscreen
Avbenzone
What makes a good UVA And UVB protection sunscreen
Octocrylene, titanium dioxide, zinc oxide and mexoryl
What are the negative effects of x rays
Cell damage and cancer
What are the negative effects of gamma rays
They can change DNA, which can promote cancer
What are the negative effects of cell phones and micro radiation
Cellphones have been linked to brain cancer (although there is no concrete proof to this)
What does the wave model explain
It explains electromagnetic radiation as alternating electric and magnetic fields that oscillate perpendicular with the direction of movement and each other.
What does quantisation mean
It means a quantity consists of quantities that cannot be made smaller
What is a quantum
An indivisible amount of a physical quantity
What are the assumptions that Max Planck made in 1901
- energy is radiated in separate packets of energy that he calle do quanta
- each quantum carries a certain amount of energy E which is equal to hf, where h is the universal constant 6,626 x 10^-34 and f is the frequency of the radiation
- the quantity energy in each quantum is directly proportional to the frequency of the radiation
- a quantum cannot be divided, you can only radiate and absorb an integer number quanta
- this energy is propagated through space as electromagnetic waves
What is the relationship between energy and the wavelength
Energy is inversely proportional to the wavelength
How do different animals behave to impending natural distasters
Dogs growl or bite their owners
Sharks go deeper into the sea
Elephants trumpet louder and move to upland areas
Frogs gather in thousands and vacate
Rodents flee their hopes
What is reflection and give an example
Waves Bouncing off a surface eg mirror
What is refraction and give an example
Waves bending after penetrating water eg spoon in water
What is the formula for momentum
P = mv
What is the SI unit for momentum
Kg.m.s^-1
