P6 Transverse and Longitudinal Waves (page 218) Flashcards
Waves transfer energy from one place to another without transferring what?
any matter (stuff)
What direction do waves transfer energy?
in the direction they are travelling.
When waves travel through a medium, what happens to the particles of the medium?
they oscillate and transfer energy between each other (see page 167). But overall the particles stay in the same place - only energy is transferred.
If you drop a twig into a calm pool of water, what happens?
ripples form on the water’s surface.
Do the ripples carry the water (or the twig) away from with them?
No
If you strum a guitar string and create soundwaves,do the soundwaves carry the air away from the guitar and create a vacuum?
No
What is meant by the amplitude of a wave?
it is the maximum displacement of a point on the wave from its undisturbed position.
Explain what the wavelength is?
it is the distance between the same point on two adjacent waves (e.g. between the rough of one wave and the trough of the wave next to it.
(see diagram 1 on page 218).
Explain what ‘frequency’ is regarding waves?
the frequency is the number of complete waves passing a certain point per second.
How is Frequency measured?
in hertz (Hz). 1 Hz is 1 wave per second.
From the frequency, you can find the period of a wave using what equation?
Period (s) T = 1
___
f - Frequency (Hz)
see diagram 2 on page 218.
(this is the amount of time it takes for a full cycle of the wave).
All waves are either what?
Transverse or Longitudinal.
What is Transverse Waves?
the oscillations (vibrations) are perpendicular (at 90°) to the direction of energy transfer.
(transverse waves have sideways vibrations). see diagram 3 on page 218).
Are most waves transverse?
Yes.
Give examples of transverse waves?
All electromagnetic waves, e.g. light (p.220)
Ripples and waes in water (p.219)
A wave on a string.
What is Longitudinal Waves?
the oscillations are parallel to the direction of energy transfer.
(longitudinal waves have parallel vibrations).
Give an example of sound waves in air?
e.g. If you push the end of a spring you get a longitudinal wave. Vibrations in the same direction as wave travels.
(see diagram 4 on page 219).
Give some examples of mechanical waves?
Water waves
shock waves
waves in springs and ropes
are all examples of mechanical waves.
What is means by ‘the wave speed’?
the speed at which energy is being transferred (or the speed the wave is moving at).
What is the Wave equation (this applies to all waves?
V = fλ
v - Wave speed (m/s)
f - frequency (Hz)
λ - wavelength (m)
see diagram equation on page 218
A radio wave has a frequency of 12.0 x 10⁶ Hz.
Find its wavelength. (the speed of radio waves in air is 3.0 x 10⁸ m/s)
λ = v ÷ f
= (3.0 x 10⁸) ÷ (12.0 x 10⁶) = 25 m
A wave has a speed of 0.15 m/s and a wavelength of 7.5 cm. Calculate its frequency (4 marks)
7.5 ÷ 100 = 0.075 m (1 mark)
wave speed = frequency x wavelength, so frequency = wave speed ÷ wavelength (1 mark)
= 0.15 ÷ 0.075 (1 mark)
= 2 Hz (1 mark)
