Waves and work power Flashcards
What is a transverse wave?
A wave where the vibration (oscillation) is at 90° (perpendicular) to the direction of wave travel and energy transfer
What are some examples of transverse wave?
All of the EM spectrum (radio waves, microwaves, infrared radiation, visible light, ultraviolet, x-rays, gamma rays), water waves, waves when shaking a slinky from side to side, waves on a rope
What is a longitudinal wave?
A wave where the vibration (oscillation) is the same direction (parallel) to the direction of wave travel and energy transfer
What are some examples of longitudinal waves?
Sound, ultrasound
What are the similarities and differences between longitudinal and transverse waves?
Similarities: All transfer energy, All can be reflected, refracted and diffracted, all involve a vibration/oscillation
Differences: Transverse vibrate 90° to direction of travel, longitudinal vibrate in the same direction as direction of travel
What is a wave?
Something that transfer energy without a (net/overall) transfer of matter (particles)
What is the amplitude of a wave?
The maximum distance travelled by a vibration/wave from its resting position (remember to measure from middle of the wave!!)
What is the wavelength of a wave?
The distance travelled by one complete wave (peak to peak or trough to trough distance)
What is the frequency of a wave?
The number of waves per second
What is the time period of a wave?
The time then for one COMPLETE wave to pass
What is the unit of FREQUENCY?
Hertz, Hz
What are the similarities of electromagnetic waves?
They are all TRANSVERSE and travel at the SAME SPEED in a vacuum (the speed of light), they all TRANSFER ENERGY and can travel through a VACUUM
What are the differences between electromagnetic waves?
They all have different FREQUENCIES and WAVELENGTHS
What is the EM spectrum in order of decreasing wavelength (and increasing frequency)?
Radiowaves, Microwaves, Infrared radiation, Visible light, Ultraviolet, X-rays, Gamma rays (learn song!!)
What are the colours of visible light in order of decreasing wavelength (and increasing frequency)?
Red, Orange, Yellow, Green, Brown, Indigo, Violet (ROYGBIV)
What are the uses of the different parts of the EM spectrum?
Radio waves: Broadcasting and communications
Microwaves: Cooking and satellite transmissions
Infrared: heaters and night vision equipment
Visible light: optical fibres and photography
Ultraviolet: fluorescent lamps used to detect forged bank notes, sterilising drinking water
X-rays: Observing the internal structures of objects and materials and medical applications
Gamma rays: Sterilising food and medical equipment, killing cancer cells, detecting cancer cells
How do microwaves cook your food?
The microwaves make the water molecules in food vibrate, causing them to heat up
How does UV light detect forged bank notes?
The UV light is absorbed by special ink on the notes and then re-emitted (released) as visible light so you can see it. This is called FLUORESCING.
How do Gamma rays, X rays and UV cause cancer and kill cells
They are IONISING and makes parts of the cell chemically reactive that shouldn’t be. So unexpected chemical reactions happen, usually killing the cell but sometimes causing mutations in your DNA that led to cancer.
What are the dangers of microwaves, infrared radiation, UV and gamma rays? How would you protect yourself?
MICROWAVES: internal heating of body tissue (internal burns) Put the microwaves in protective cases so they do not pass through you, close microwave door.
INFRARED: skin burns. Wear protective clothing, do not expose yourself for too long.
ULTRAVIOLET: damage to surface cells and blindness (skin cancer) Wear protective clothing/sun cream and UV protective sunglasses.
GAMMA RAYS/X-RAYS: cancer, mutation. Put gamma rays in lead casing so they cannot get out. Do not expose yourself for a long time, try to work from a different room. Monitor exposure using a film badge
What two things can happen to a wave when it encounters a new material?
Reflected or refracted
What is the Law of Reflection
Angle of incidence = Angle of reflection
What is the normal line?
An imaginary line that is drawn at 90° to the surface where the ray hits it.
Where are the angles of incidence and reflection measured from?
The angles are always measured between the normal line and ray
