EM spectrum, Reflection and Refraction Flashcards
Order of waves from long to short wavelength(low to high frequency)
-Sing the song
Radio waves, Microwaves, Infrared (radiation), Visible Light, Ultraviolet, X-rays, Gamma rays
What is the EM spectrum
A continuous range of wavelengths/frequencies of electromagnetic waves/radiation (with different uses)
How fast do all these waves travel
300,000,000 m/s
Uses and dangers of Radio waves
1 Broadcasting on radio or TV
2 communication and satellite transmission
3 Radar
- heats up body tissue
Uses and dangers of Microwaves
1 Microwave ovens (heating foods)
2 Satellite communication
-heats up body tissue (specifically water)
-burns
Uses and dangers of Infrared
1 heating
2 thermal imaging
3 remote controls
-heating
-skin absorption
Uses and dangers of Visible Light
- seeing and taking photos
- Fibre optic communications
-eye damage
Uses and dangers of Ultraviolet
1 fluorescent lights
2 sterilisation
3 verifying money, ID, passports
-skin damage (sunburns)
-eye damage (cataracts)
skin cancer (wear sun cream)
Uses and dangers of X-rays
1 medical imaging
2 security screening
-damage cells
-ionising radiation can cause cancer risk
-acute radiation sickness
can be blocked by lead screen
Uses and dangers of Gamma rays
1 medical imaging
2 cancer treatment
-damage cells
-ionising radiation can cause cancer risk
-acute radiation sickness
can be blocked by lead screen or sometimes concrete
Similarities of all EM waves
All travel at speed of light
All transverse waves
All waves can be:
Reflected and refracted
Law of reflection
Angle of incidence (i) = Angle of reflection (r)
Less dense to more dense
Light bends towards normal
Passing along the normal
Light does not bend at all
Snell’s Law (refractive index)
n (refractive index) = sini/sinr
Total Internal Reflection + uses
Occurs when the angle of incidence is less than the critical angle;
and the incident material is denser than the second material
Optical fibres, prisms e.g periscopes
Critical Angle and formula
Angle of incidence where refraction along the boundary occurs (90°)
sinc = 1/n (refractive index)
Doppler Effect definition
The apparent change in wavelength and frequency of a wave emitted by a moving source
Explain the Doppler Effect
-Usually when a stationary object emits waves, the waves spread out symmetrically
-When the object moves, the waves get squashed together at one end, and stretched at the other end
-To an observer at the front of the object, the wavelength appears to be smaller and vice versa
= The wavelength decreases at the front (and vice versa)
How do ray guns measure the speed of a car
The ray gun emits a wave at a known frequency and reflects off the car back to the device
Because the car is moving, the frequency shifts due to the Doppler effect as the wavefronts appear more condensed/apart
The ray gun compares it to the original frequency of the wave, and calculates the speed of the car
