Topic P6 - Waves Flashcards
What happens when waves travel through a medium?
They transfer energy (not matter)
Frequency definition
Number of complete waves passing a certain point each second
Period definition
Amount of time it takes for a complete wave to pass a point
Sound moves away…
the air particles don’t
Ripple on waters surface move away…
The water doesn’t
What is amplitude?
Maximum displacement of a point on a wave from its rest position
What is wavelength?
Length of a full cycle of a wave
What can happen when a wave hits a boundary?
- It can be absorbed
- Transmitted
- Reflected
What are transverse waves?
Oscillations perpendicular (at 90 degrees) to direction of energy transfer
What are the three types of transverse waves?
- Ripples In water
- Electromagnetic waves e.g light
- Waves on a string
What are longitudinal waves?
Oscillations parallel to direction of energy transfer.
Examples of longitudinal waves?
Sound waves
What is the WAVE EQUATION?
wave speed = frequency x wavelength
What is wave speed measured in?
m/s
What is frequency measured in?
Hertz, Hz
What is wavelength measured in?
meter
1 __ is 1 wave per second
1 Hz
How do you measure the Speed of Sound?
1) Speaker attached to signal generator of specific frequency
2) microphones attached to oscilloscope
Waves detected at each microphone shown as separate waves.
Move one microphone until waves line up. Distance between microphones is now equal to one wavelength
Use Wave Equation to find speed
Refraction definition
When a wave changes direction as it crosses a boundary between two materials at an angle to the normal.
What happens if a wave refracts and slows down?
- The wavelength decreases
- Bends towards normal
What happens if wave refracts and speeds up?
- Wavelength increases
- Bends away from normal
What happens to frequency in refraction?
It never changes
What happens to wave fronts after refraction?
Wave fronts are closer together after refraction as wavelength has decreased
What is the angle of incidence in refraction?
The angle between the incoming ray and the normal
What is the angle of refraction?
The angle between the normal and the angle of refraction
What is on the ELECTROMAGNETIC SPECTRUM (EM)?
- Radio Waves
- Microwaves
- Infrared
- Visible Light
- Ultraviolet
- X-rays
- Gamma Rays
What is an EM spectrum mnemonic?
- Raging
- Martians
- Invaded
- Venus
- Using
- X-ray
- Guns
What colour does the Electromagnetic Spectrum go from (left to right)?
Red -> Violet
What happens as the Electromagnetic Spectrum increases?
Increasing frequency
Decreasing Wavelength
The EM spectrum is continuous
True or False?
True
What are three EM wave characteristics?
- Are transverse
- Transfer energy from source to absorber
- Travel at same speed in air or vacuum
Can our eyes detect Infrared light?
No. We can only detect Visible Light.
How are Gamma Rays created through nucleus?
Gamma rays created by changes in atom’s nucleus.
How do you produce Radio Waves?
- Alternating Current supplied to transmitter.
- Electrons oscillate, producing radio waves
- Emitted radio waves transfer energy to the receiver
- Radio waves absorbed, causing electrons in receiver to oscillate
- Alternating current of same frequency as radio waves induced in receiver.
What are the uses of Radio Waves?
- TV
* Radio
What are the uses of Microwaves?
- Satellite Communications
* Cooking
What are the uses of Infrared Radiation?
- Electric Heaters
- Cooking (Toasters)
- Infrared Cameras
What are the uses of Visible Light?
• Communications through optical fibres
What are the uses of UV waves?
- Energy efficient lights
* Sun tan beds
What are the uses of X-rays and gamma rays?
- Medical imaging
* Medical treatments
Radiation Dose definition
Measure of the risk of harm to body tissues due to exposure to radiation. It is measured in sieverts.
What does risk of EM waves depend on?
Risk depends on:
• Size of dose
• Type of radiation
What are the 2 types of ionising radiation?
- UV
* X-rays and gamma rays
Harmful effects of UV on human body tissue?
- Can prematurely age skin
* Increases risk of skin cancer
Harmful effects of X-rays and gamma rays on human body tissue?
- Gene mutation
* Cancer
