3 Waves Flashcards
Transverse Waves - oscillations
Oscillations are perpendicular to the direction of energy transfer
Longitudinal Waves - oscillations
Oscillations are parallel to the direction of energy transfer
Example of Transverse Waves
Electromagnetic Waves
e.g. light
Example of Longitudinal Waves
Sound waves
Amplitude
Height of the wave
Wavefront
Frequency
Number of complete waves per second
Wavelength
The distance for one complete wave
Time Period
Time for one complete wave
What do waves transfer/not transfer
Transfer energy and information without transferring matter
Equation for Wavespeed
Frequency x Wavelength
Equation for Frequency
1/ Time Period
What can be done to all waves
Reflected
Refracted
Doppler Effect
There is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer
What is light part of?
A continuous spectrum -> electromagnetic spectrum
Order of electromagnetic spectrum
Increasing frequency / low wavelength
Radio Waves
Microwaves
Infrared Radiation
Visible Light (ROYGBIV)
Ultraviolet
X-Ray
Gamma Rays
Uses of Radio Waves
broadcasting and communications
Uses of Microwaves
cooking and satellite transmissions
Uses of Infrared Radiation
heaters and night vision equipment
Uses of Visible Light
optical fibres and photography
Uses of Ultraviolet
fluorescent lamps
Uses of X - Rays
observing the internal structure of objects and materials, including for medical applications
Uses of Gamma Rays
sterilising food and medical equipment
Dangers of microwaves
internal heating of body tissue
Dangers of Infrared Radiation
skin burns
Dangers of Ultra Violet
damage to surface cells and blindness
Dangers of Gamma rays
cancer, mutation
Law of Reflection
the angle of incidence = the angle of reflection
Refraction
A change in direction of a wave passing from one medium to another due to a change of speed
What happens when a light ray is passing from a medium of low refractive index (e.g. air) to a medium of high refractive index (e.g. water)?
Fast -> Slow
Water has a higher refractive index + more optically dense than air.
So refracted ray bends towards normal
What happens when a light ray is passing from a medium of high refractive index (e.g. water) to a medium of low refractive index (e.g. air)?
Slow -> Fast
Air has a lower refractive index + less optically dense than water.
So refracted ray bends away from the normal
Formula for Refractive Index
Refractive index = sin (angle of incidence)/sin(angle of refraction)
Critical Angle
When the angle of incidence is greater than the critical angle, the light ray stops being refracted and is totally internally reflected (TIR)
Formula for critical angle
sin (critical angle) = 1/refractive index
Total internal reflection in a prism - use
Reflectors on the back of vehicles
Reflective clothing
Total internal reflection in optical fibres - use
Fibre broadband (communications)
Endoscopes
Frequency range for human hearing
20 Hz - 20 000 Hz
Upper limit decreases with age
Investigating the speed of sound in air
2 people stand 100m away from eachother
Person A should clap their hands
Person B should use a stopwatch (start when they see person A clap hands and stop when they hear the sound)
Speed = distance/time
Repeat with multiple distances
Frequency and pitch
As frequency increases, pitch increases
Amplitude and loudness
As amplitude increases, loudness increases
Practical: investigate the frequency of a sound wave using an oscilloscope
- Connect 2 microphones to an oscilloscope and place them 2m apart
- Clap
- Find the time difference between the 2 peaks of the 2 graphs for the 2 microphones
- Speed = distance/time
Characteristics of all electromagnetic waves
- Travel at the speed of light = 3 x 10 to the power of 8
- All are transverse
- Can travel in a vacuum/don’t need a medium
- Can be reflected + refracted
Total Internal Reflection (TIR)
- All reflection is inside the material
- All the light is reflected
- Occurs when the angle of incidence is greater than the critical angle
Virtual Image
- Cannot be formed on a screen
- Laterally inverted
Conditions for Total Internal Reflection
- Light travels froma. more optically dense to a less optically dense medium (slow-> fast)
- i>c