6: Waves Flashcards
What is the difference between transverse and longitudinal waves.
Transverse waves have oscillations perpendicular to the direction of travel.
Longitudinal waves have oscillations parallel to the direction of travel.
Define the amplitude of a wave.
The amplitude of a wave is the maximum displacement of a point on the wave away from its undisturbed position.
Define the wavelength of a wave.
The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave.
Define the frequency of a wave.
The frequency of a wave is the number of waves passing a point each second.
What is the equation for calculating the period of a wave?
T = 1/ƒ
T: Period (seconds, s)
ƒ: frequency (hertz, Hz)
What is wave speed and what is the equation for calculating it?
The wave speed is the speed at which energy is transferred (or the wave moves) through the given medium.
v = ƒλ
v: wave speed (metres per second, m/s)
ƒ: frequency (hertz, Hz)
λ: wavelength (metres, m)
List the electromagnetic spectrum from longest to shortest wavelength.
—Long wavelength, Low frequency—
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-Rays
Gamma rays
—Short wavelength, High frequency—
What are four ways electromagnetic waves can interact with substances
Different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary in wavelength.
Some effects, for example refraction, are due to the difference in velocity of the waves in different substances.
What are some of the electrical properties of radio waves?
Radio waves can be produced by oscillations in electrical circuits.
When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so the radio waves can themselves induce oscillations in an electrical current.
What is the unit of radiation dose?
Sievert (Sv)
Required Practical Activity 20.1: What equipment is required to observe water waves in a ripple tank?
- a ripple tank plus accessories
- a low voltage power supply
- a lamp
- a metre ruler
Required Practical Activity 20.1: State a method you could use to observe water waves in a ripple tank.
1: Set up the ripple tank as shown in the diagram
—(Diagram WILL be provided)—
2: Pour water to a depth of about 55mm into the tank.
3: Adjust the height of the wooden rod to that it just touches the surface of the water
4: Switch on the overhead lamp and the electric motor.
5: Adjust the speed of the motor to produce low frequency water waves.
6: Adjust the height of the lamp so that the pattern of the waves can be clearly seen on the white card.
7: Place a metre ruler at right angles to the waves shown in the pattern on the card.
Measure across as many waves as you can. Then divide that length by the number of waves. This gives the wavelength of the waves. Record this value in a table
8: count the number of waves passing a point in the pattern over a given time (say 10 seconds).
Then divide the number of waves counted by 10. This gives the frequency of the waves. Record this value in a table
9: Calculate the speed of the waves using the equation:
wave speed = frequency x length
10: Record this value in a table
Required Practical Activity 20.2: What apparatus is required to observe waves in a solid?
- a vibration generator
- 5 or 6 watt signal generator (power supply)
- a string or piece of elasticated cord
- a 100g weight stack
- a wooden bridge
- a pulley on a clamp
Required practical activity 20.2: State a method you could use to observe waves in a solid.
1: Set up the apparatus as shown in the diagram.
—(Diagram WILL be provided)—
Attach one end of the elasticated cord to the vibration generator that is connected to the power supply. Attach the other end of the elasticated cord to the weight stack and have it run through the pulley and then the wooden bridge.
—(This information is not required, )—
—(it is just here for reference)—
2: Switch on the vibration generator. the string (or elasticated cord) should start to vibrate.
3: To see a clear wave pattern, adjust the tension in the string or move the wooden bridge to adjust the length of the string.
The waves should look like they are not moving
4: Use a metre ruler to measure across the as many half wavelengths as possible (a half wavelength is one loop).
Then divide the total length by the number of half waves. Multiplying this number by two will give the wavelength.
5: The frequency of the wave is the frequency of the signal generator (power supply).
6: Calculate the speed of the wave using the equation:
Wave speed = frequency x wavelength
7: Repeat steps 2-6 for different frequencies.
