Unit 3 - Lesson 2: Waves and the EM Spectrum Flashcards
What do all waves carry?
Energy
What do waves transfer?
Energy
How do waves move?
Waves vibrate or oscillate.
What two types of waves are there?
Transverse and Longitudinal.
Describe the movement of a transverse wave.
Vibrations are from side to side at right angles (90 degrees) to the direction of travel.
Describe the movement of a longitudinal wave.
There is one wavelength. There are compressions and rarefactions. Vibrations are in the same direction as wave is travelling.
Give examples of transverse waves.
Any wave from the electromagnetic spectrum (including visible light):
(In order)
- Radio Waves
- Microwaves
- IR
- Visible Spectrum (Rainbow on the electromagnetic spectrum)
- UV
- X-rays
- Gamma-rays
Give an example of longitudinal waves.
Sound. As longitudinal waves travel forward, they vibrate in the same direction as the wave is travelling.
What are the properties of transverse waves? Provide/draw a diagram.
DIAGRAM: https://i.pinimg.com/736x/06/e1/b3/06e1b301ce43df0b3cfaf6f2658ab628.jpg
Transverse waves have a peak or crest.
Transverse waves have a middle (rest).
Transverse waves have a trough.
Wavelength (λ) - In transverse waves, this is the distance from one peak to the next.
What are the properties of longitudinal waves? Provide/draw a diagram.
DIAGRAM: https://i.pinimg.com/736x/b8/11/97/b81197f3cffaa7944922514d8502829f.jpg
Longitudinal waves have compression at the start and end.
Longitudinal waves have rarefaction in the middle.
Longitudinal waves have wavelength.
Longitudinal waves have amplitude in the centre.
Wavelength (λ) - In longitudinal waves, this is the distance from one compression to the next.
What is frequency (f)? What can change the frequency of a wave?
Frequency is the number of waves (passing a set point) per second. It’s measured in hertz (Hz). The only thing that can change the frequency of a wave is its source.
What is period (T)?
Period is the time taken in seconds for one complete wave to pass a point.
What is amplitude?
Amplitude is the height of waves (from rest to crest).
What is speed?
Speed is how fast the wave is moving.
What is velocity (v)?
Velocity is how fast the wave is moving in a given direction.
How can we convert Hz into kHz?
Divide Hz by 1000.
How can we convert kHz into Hz?
Multiply kHz by 1000.
How can we convert kHz into MHz?
Divide kHz by 1000.
How can we convert MHz into kHz?
Multiply MHz by 1000.
What is the equation for calculating wave speed? Give your answer in word units and algebraic symbols.
Word Units:
Speed (m/s) = Frequency (Hz) x Wavelength (m)
Algebraic Symbols:
V = f x λ
What is the equation for calculating frequency or time period?
Frequency = 1/Time Period
OR
Period = 1/Frequency
What is created when many waves travel in the same direction together?
A wavefront.
What is a wavefront?
These are planes (like a flat sheet) joining all the points of the wave, that are vibrating, together.
What is the distance between each wavefront equal to?
The distance between each wavefront is equal to one wavelength.
How can we show wavefronts? What can we use?
We can show wavefronts using a ripple tank.
How are uniform waves created?
Uniform waves are created in a tank of water by a paddle that is dipped into the water at regular intervals via a motor. A light shone down through the waves projects their shadow onto a screen below. A wavefront is a line where the water is affected by the wave in the same way at the same time. The wave crests are a part of the wavefront where the water is lifted to its maximum displacement (movement from its original position).
Provide a picture/sketch of the way in which uniform waves are created.
https://i.pinimg.com/736x/eb/13/bf/eb13bfa924dfd0400197af8428223c4a.jpg
When waves are forced through a large opening, what do we see?
When waves are forced through a large opening, we see plane (straight) wavefronts.
What happens to the wave’s shape as the gap/opening gets smaller?
The smaller the gap, the more curved the waves become.
Does the distance between wavefronts change as they move through a gap/opening?
No. The distance between wavefronts does not change as they move through the gap.
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What is the Electromagnetic (EM) Spectrum?
The electromagnetic (EM) spectrum is a list of transverse waves organised in order of their wavelength and frequency.
What do we call the waves on the electromagnetic spectrum?
Electromagnetic waves OR radiation.
In what order is the electromagnetic spectrum? Give a mnemonic too.
Radio → Microwave → Infrared → Visible → Ultraviolet → X-ray → Gamma Ray
Mnemonic: Raging Monkeys Invade Venus Using X-ray Guns.
What are the frequencies (Hz) of the electromagnetic waves in the electromagnetic spectrum?
Radio: 10^4
Microwave: 10^8
Infrared: 10^12
Visible: 10^15
Ultraviolet: 10^16
X-Ray: 10^18
Gamma Ray: 10^20
What is the wavelength (meters) of each electromagnetic wave in the electromagnetic spectrum?
Radio: 10^3
Microwave: 10^-2
Infrared: 10^-5
Visible: .5 x 10^6
Ultraviolet: 10^-8
X-ray: 10^-10
Gamma Ray: 10^-12
Does wavelength decrease or increase from radio to gamma rays?
Wavelength decreases.
Does frequency decrease or increase from radio to gamma rays?
Frequency increases.
Can the amplitude of EM waves change?
Yes.
Is wave speed the same or different for all transverse waves in free space (a vacuum)?
Wave speed is the same for all transverse waves in free space (a vacuum). This is the speed of light (because it’s an example of EM radiation).
What is the speed of light? Give your answer in m/s, km/s, and km/h.
3 x 10^8 m/s.
In km/s, the speed of light is exactly 299,792.458 in vacuum. It’s approximately 300,000 km/s.
In km/h, the speed of light is 1,080,000,000.
Give two examples of mediums in which speed can change.
Air and wave.
Which EM radiation can be seen with the naked eye?
Visible light.
What colours does visible light come in?
All the colours of the rainbow
Does each colour have a different wavelength?
Yes
What is an object’s colour dictated by?
The wavelengths it absorbs and reflects.
What does the eye absorb when perceiving colour?
The reflected colour.
What is the order of colour in visible light? Give a mnemonic.
Red, Orange, Yellow, Green, Blue, Indigo, Violet
Richard, Of, York, Gave, Battle, In, Vain
Which colour in visible light has the longest wavelength and lowest frequency?
Red light has the longest wavelength and lowest frequency.
Which colour in visible light has the shortest wavelength and highest frequency?
Violet light has the shortest wavelength and highest frequency.
