P6 - Waves Flashcards
Waves
Waves transfer energy without the net movement of matter
What is amplitude?
What is wavelength?
Amplitude is the maximum displacement of a point on a wave from its undisturbed
Wavelength is the distance from one point on a wave to the same point on the next wave
What is frequency?
What is period?
What is the equation for period?
Frequency is the number of waves passing a point each second
Period is the time taken (in seconds) for one whole wave to pass a point
Period = 1 / Frequency
What is a transverse wave?
What are examples of transverse waves?
In a transverse wave the vibrations/oscillations are perpendicular to the direction of energy transfer
All electromagnetic waves
Water waves
What is a longitudinal wave?
What are examples of longitudinal waves?
In a transverse wave the vibrations/oscillations are parallel to the direction of energy transfer
Sound waves
Equation for wave speed
Wave speed = frequency x wavelength
What is the electromagnetic spectrum?
longest wavelength & lowest frequency
↓ Radio wave
↓ Microwave
↓ Infrared
↓ Visible light
↓ Ultraviolet
↓ X-ray
↓ Gamma ray
shortest wavelength & highest frequency
Electromagnetic spectrum: Radio wave
What are its uses?
What are the dangers?
• Communication (radios, tv)
• No known danger
Electromagnetic spectrum: Radio wave
Radio waves in electrical circuits
Radio waves are produced by oscillations (changes in current & potential difference) in electrical circuits
A metal rod can be used as an aerial to receive the signal
The radio waves are absorbed causing an alternating current with the same frequency as the wave
Electromagnetic spectrum: Microwave
What are its uses?
What are the dangers?
• Heating food
• Communication (satellites, wifi, phones)
• Possible heat damage to internal organs
Electromagnetic spectrum: Infrared
What are its uses?
What are the dangers?
• Remote controls
• Electrical heaters
• Motion sensor
• Infrared cameras
• Short range communication
• Skin burns
Electromagnetic spectrum: Visible light
What are its uses?
What are the dangers?
• Seeing & taking pictures
• Fibre optic
• Communication
• Bright light causes eye damage
Electromagnetic spectrum: Ultraviolet
What are its uses?
What are the dangers?
• Getting a sun tan
• Fluorescent bulbs
• Eye damage
• Sun burn & skin cancer
Electromagnetic spectrum: X-ray
What are its uses?
What are the dangers?
X-rays are absorbed by bones & pass through skin & muscle
• X-ray images (medical, airport security)
• Kills cells mutations cancer
Electromagnetic spectrum: Gamma ray
How is it produced?
What are its uses?
What are the dangers?
Gamma rays are produced when the nucleus of an atom changes from unstable to stable
• Treating cancer
• Sterilising medical equipment
• Kills cells mutations
• Mutations
• Cancer
Electromagnetic waves:
What happens when an EM wave hits an atom?
What happens when an atom emits an EM wave?
• The electron absorbs it
• The electron gains energy & moves up an energy level (shell)
The electron moves down an energy level (shell)
Infrared required practical:
What is the best emitter of radiation?
What is the best absorber of radiation?
Emit = lets heat pass through
Absorb = takes heat in
Best emitter of radiation
Best absorber of radiation
↓ Matt black (biggest temp change)
↓ White
↓ Silver
Worst emitter of radiation
Worst absorber of radiation
What is refraction?
When waves enter a different medium (e.g. air, water, glass) they can change direction.
The change in direction is Refraction.
What is the Normal?
What is the Angle of Incidence?
What is the Angle of Refraction?
Angle of Incidence
Normal
= a line perpendicular to the surface
How does the speed change due to refraction?
When a wave moves to another medium its speed changes.
Example - if a car slows down it bends towards the normal & if a car speeds up it bends away from the normal
What changes the speed of light?
Energy of light depends on its frequency
E infinity f
The frequency of light always stays the same
V = f something
When light slows down its wavelength decreases & frequency stays the same
Longer wavelength = higher speed
Shorter wavelength = lower speed
