Waves Flashcards
Electromagnetic Spectrum sentence
Rich Men In Vegas Use Xpensive Glasses DWIF
Electromagnetic spectrum
Radio
Micro
Infrared
Visible
Ultraviolet
X-ray
Gamma
What does DWIF stand for
Decreasing Wavelength Increasing Frequency
Uses for Radio Waves
Radio and TV communication
Uses for Micro Waves
Satellite Communication and Cooking
Uses for Infrared Waves
Heaters and Night vision equipment
Uses for Visible Waves
Human sight
Uses for Ultraviolet Waves
Fluorescent lamps
Uses for X-ray Waves
Medical imaging and security
Uses for Gamma Waves
Sterelising food or medical equipment
Speed of electromagnetic waves is
the same in a vacuum and roughly the same in air
Critical angle is when
the refracted beam runs along the line between the two mediums
Total internal reflection is when the
angle of incidence is sufficiently large such that the beam does not refract but reflects back into the object
Total internal reflection occurs when
angle of incidence > critical angle
sin (critical angle) =
1/optical density or 1/n
Optical fibres are
- thin rods of glass
- which use total internal reflection
- to transfer information using light
Uses of Optical fibres
- medicine - e.g. endoscopes
- communications - e.g. data transfer
Hazards of Microwaves
Internal heating of body tissue
Hazards of Infrared waves
Skinburn
Hazards of Ultraviolet waves
Skin cancer and blindness
Hazards of X-rays
Mutations leading to cancer
Hazards of Gamma waves
Mutations leading to cancer
To estimate the speed of sound in air
- Make a noise at a known large distance form a solid wall
- Record the time taken for the echo to be hear
- Use speed=distance/time, where distance is twice the length as the sound had to go there and back
Waves transfer
energy and information without transferring matter
Transverse waves have
- Peaks and troughs
- Vibrations perpendicular to the direction of travel
Example of Transverse waves
Light
Longitudinal Waves have
- Compressions (particles pushed together) then Rarefactions (particles moved apart)
- Vibrations parallel to the direction of travel
Example of Longitudinal waves
Sound
Quiet, low pitch longitudinal waves have
a small amplitude and a long wavelength
Loud, high pitch longitudinal waves have
a big amplitude and a short wavelength
Amplitude
Distance from equilibrium point to maximum or minimum point
Wavefront
Line through points that are at the same point in their wave cycle
Frequency (f)
Number of waves per second
Frequency is measured in
Hertz (Hz)
Wavelength (lamda)
distance between corresponding points on adjacent waves
Time period (T)
time for a wave to pass a fixed point
Frequency eqauls
1/Time period
Speed of a wave equals
Frequency x Wavelength
The Doppler effect explanation
- If the wave source is moving relative to an observer
- The observed frequency and wavelength will change
- When moving towards, the waves will be bunched together leading to a shorter wavelength, greater frequency and higher pitch
- When moving away, the waves will be more spaced apart, leading to longer wavelength, lower frequency and lower pitch
Can all waves be reflected?
Yes
With reflection, angle of incidence equals
the angle of reflection
When a wave is reflected these remain unchanged
Frequency, Wavelength and Speed
Can all waves be refracted?
Yes
Refraction occurs when a wave enters…
…a medium of a different density
The process of refraction when entering a medium of a lower density
- Speed increases
- Wave bends away from the normal
- Incidence angle is less than the refracted angle
The process of refraction when entering a medium of a higher density
- Speed decreases
- Wave bends towards the normal
- Incidence angle is greater than the refracted angle
With Refraction, this remains unchanged
Frequency
With Refraction, these two things change
Wavelength and Speed
