P5.2.1-2 Flashcards
List the electromagnetic spectrum in order.
Radio waves (lowest freq) (highest wavelength 10^2)
Microwaves
Infrared radiation
Visible light
Ultra violet
X rays
Gamma rays (high frequency) (low wavelength 10^-16)
What do electromagnetic waves consist of?
Oscillating electric and magnetic fields
- The fields oscillate perpendicular to the direction of the wave
What EM wave can our eyes detect?
Visible light
At what speed do all EM waves travel at in a vacuum (ie space)?
3*10^8m/s
How do EM waves transfer energy?
From source to absorber
- Eg microwaves sent to satellite
How do you produce radio waves?
Oscillating pd across wire, electrons move back and forward, produces a changing magnetic field and electric field which is emitted as a radio wave
How do you detect radio waves?
When the field/wave meets a metal object (e.g. aerial), this moves its electrons producing an electrical signal.
Give some uses of microwaves.
- Phone communication
- WiFi, bluetooth, satellites
Microwave oven - water and lipids absorb microwaves, heating the food. Heat transferred to the middle via conduction
Give some uses of radio waves.
TV and radio stations transmit sound and picture information with radio waves
Give some uses of IR.
Remote control use IR pulses to communicate with televisions
Send information at high speed down optical fibres
Cooks food in a grill or oven
Give a use of visible light.
Ships communicate via visible light flashing for
Lasers in CDs, DVDs, Blu-rays
Give some uses of UV light.
Produce vitamin D - need for bones
UV light detects foreign bank notes, and bodily fluids
In what ways are UV, X-rays and gamma rays useful?
UV: sterilises water (kills bacteria)
X rays: kill skin cancer cells
Gamma: kill bacteria and cancer cells
Which waves are dangerous and why?
UV: damage DNA, cause uncontrolled division = cancer
- If eye is exposed to too much UV, cataract occurs (cloudy cornea)
X ray: damage cells, cancer - radiographers stand behind the screen so they aren’t affected
Gamma: damage and kill cells
