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A cork on the surface of a swimming pool bobs up and down once every second on some ripples. The ripples have a wavelength of 20 cm . If the cork is 2 m from the edge of the pool, how long does it take a ripple passing the cork to reach the edge?

  1. We are given:

    • frequency of wave: f = 1 Hz
    • wavelength of wave: λ = 20 cm
    • distance of cork from edge of pool: D = 2 m

    We are required to determine the time it takes for a ripple to travel between the cork and the edge of the pool.

    The wavelength is not in SI units and should be converted.

  2. The time taken for the ripple to reach the edge of the pool is obtained from:

    t = D v ( from v = D t )

    We know that

    v = f · λ

    Therefore,

    t = D f · λ
  3. 20 cm = 0 , 2 m
  4. t = D f · λ = 2 m ( 1 Hz ) ( 0 , 2 m ) = 10 s
  5. A ripple passing the leaf will take 10 s to reach the edge of the pool.

The following video provides a summary of the concepts covered so far.

Khan academy video on waves - 1

Waves

  1. When the particles of a medium move perpendicular to the direction of the wave motion, the wave is called a ... ... ... wave.
  2. A transverse wave is moving downwards. In what direction do the particles in the medium move?
  3. Consider the diagram below and answer the questions that follow:
    1. the wavelength of the wave is shown by letter .
    2. the amplitude of the wave is shown by letter .
  4. Draw 2 wavelengths of the following transverse waves on the same graph paper. Label all important values.
    1. Wave 1: Amplitude = 1 cm, wavelength = 3 cm
    2. Wave 2: Peak to trough distance (vertical) = 3 cm, peak to peak distance (horizontal) = 5 cm
  5. You are given the transverse wave below.
    Draw the following:
    1. A wave with twice the amplitude of the given wave.
    2. A wave with half the amplitude of the given wave.
    3. A wave travelling at the same speed with twice the frequency of the given wave.
    4. A wave travelling at the same speed with half the frequency of the given wave.
    5. A wave with twice the wavelength of the given wave.
    6. A wave with half the wavelength of the given wave.
    7. A wave travelling at the same speed with twice the period of the given wave.
    8. A wave travelling at the same speed with half the period of the given wave.
  6. A transverse wave travelling at the same speed with an amplitude of 5 cm has a frequency of 15 Hz. The horizontal distance from a crest to the nearest trough is measured to be 2,5 cm. Find the
    1. period of the wave.
    2. speed of the wave.
  7. A fly flaps its wings back and forth 200 times each second. Calculate the period of a wing flap.
  8. As the period of a wave increases, the frequency increases/decreases/does not change.
  9. Calculate the frequency of rotation of the second hand on a clock.
  10. Microwave ovens produce radiation with a frequency of 2 450 MHz (1 MHz = 10 6  Hz) and a wavelength of 0,122 m. What is the wave speed of the radiation?
  11. Study the following diagram and answer the questions:
    1. Identify two sets of points that are in phase.
    2. Identify two sets of points that are out of phase.
    3. Identify any two points that would indicate a wavelength.
  12. Tom is fishing from a pier and notices that four wave crests pass by in 8 s and estimates the distance between two successive crests is 4 m. The timing starts with the first crest and ends with the fourth. Calculate the speed of the wave.

Summary

  1. A wave is formed when a continuous number of pulses are transmitted through a medium.
  2. A peak is the highest point a particle in the medium rises to.
  3. A trough is the lowest point a particle in the medium sinks to.
  4. In a transverse wave, the particles move perpendicular to the motion of the wave.
  5. The amplitude is the maximum distance from equilibrium position to a peak (or trough), or the maximum displacement of a particle in a wave from its position of rest.
  6. The wavelength ( λ ) is the distance between any two adjacent points on a wave that are in phase. It is measured in metres.
  7. The period ( T ) of a wave is the time it takes a wavelength to pass a fixed point. It is measured in seconds (s).
  8. The frequency ( f ) of a wave is how many waves pass a point in a second. It is measured in hertz (Hz) or s - 1 .
  9. Frequency: f = 1 T
  10. Period: T = 1 f
  11. Speed: v = f λ or v = λ T .
  12. When a wave is reflected from a fixed end, the resulting wave will move back through the medium, but will be inverted. When a wave is reflected from a free end, the waves are reflected, but not inverted.

Exercises

  1. A standing wave is formed when:
    1. a wave refracts due to changes in the properties of the medium
    2. a wave reflects off a canyon wall and is heard shortly after it is formed
    3. a wave refracts and reflects due to changes in the medium
    4. two identical waves moving different directions along the same medium interfere
  2. How many nodes and anti-nodes are shown in the diagram?
  3. Draw a transverse wave that is reflected from a fixed end.
  4. Draw a transverse wave that is reflected from a free end.
  5. A wave travels along a string at a speed of 1,5 m · s - 1 . If the frequency of the source of the wave is 7,5 Hz, calculate:
    1. the wavelength of the wave
    2. the period of the wave
  6. Water waves crash against a seawall around the harbour. Eight waves hit the seawall in 5 s. The distance between successive troughs is 9 m. The height of the waveform trough to crest is 1,5 m.
    1. How many complete waves are indicated in the sketch?
    2. Write down the letters that indicate any TWO points that are:
      1. in phase
      2. out of phase
      3. Represent ONE wavelength.
    3. Calculate the amplitude of the wave.
    4. Show that the period of the wave is 0,67 s.
    5. Calculate the frequency of the waves.
    6. Calculate the velocity of the waves.

Questions & Answers

define electric image.obtain expression for electric intensity at any point on earthed conducting infinite plane due to a point charge Q placed at a distance D from it.
Mateshwar Reply
explain the lack of symmetry in the field of the parallel capacitor
Phoebe Reply
pls. explain the lack of symmetry in the field of the parallel capacitor
Phoebe
does your app come with video lessons?
Ahmed Reply
What is vector
Ajibola Reply
Vector is a quantity having a direction as well as magnitude
Damilare
tell me about charging and discharging of capacitors
Ahemen Reply
a big and a small metal spheres are connected by a wire, which of this has the maximum electric potential on the surface.
Bundi Reply
3 capacitors 2nf,3nf,4nf are connected in parallel... what is the equivalent capacitance...and what is the potential difference across each capacitor if the EMF is 500v
Prince Reply
equivalent capacitance is 9nf nd pd across each capacitor is 500v
santanu
four effect of heat on substances
Prince Reply
why we can find a electric mirror image only in a infinite conducting....why not in finite conducting plate..?
Rima Reply
because you can't fit the boundary conditions.
Jorge
what is the dimensions for VISCOUNSITY (U)
Branda
what is thermodynamics
Aniket Reply
the study of heat an other form of energy.
John
heat is internal kinetic energy of a body but it doesnt mean heat is energy contained in a body because heat means transfer of energy due to difference in temperature...and in thermo-dynamics we study cause, effect, application, laws, hypothesis and so on about above mentioned phenomenon in detail.
ing
It is abranch of physical chemistry which deals with the interconversion of all form of energy
Vishal
what is colamb,s law.?
Muhammad Reply
it is a low studied the force between 2 charges F=q.q`\r.r
Mostafa
what is the formula of del in cylindrical, polar media
Birengeso Reply
prove that the formula for the unknown resistor is Rx=R2 x R3 divided by R3,when Ig=0.
MAXWELL Reply
what is flux
Bundi Reply
Total number of field lines crossing the surface area
Kamru
Basically flux in general is amount of anything...In Electricity and Magnetism it is the total no..of electric field lines or Magnetic field lines passing normally through the suface
prince
what is temperature change
Celine
a bottle of soft drink was removed from refrigerator and after some time, it was observed that its temperature has increased by 15 degree Celsius, what is the temperature change in degree Fahrenheit and degree Celsius
Celine
process whereby the degree of hotness of a body (or medium) changes
Salim
Q=mcΔT
Salim
where The letter "Q" is the heat transferred in an exchange in calories, "m" is the mass of the substance being heated in grams, "c" is its specific heat capacity and the static value, and "ΔT" is its change in temperature in degrees Celsius to reflect the change in temperature.
Salim
what was the temperature of the soft drink when it was removed ?
Salim
15 degree Celsius
Celine
15 degree
Celine
ok I think is just conversion
Salim
15 degree Celsius to Fahrenheit
Salim
0 degree Celsius = 32 Fahrenheit
Salim
15 degree Celsius = (15×1.8)+32 =59 Fahrenheit
Salim
I dont understand
Celine
the question said you should convert 15 degree Celsius to Fahrenheit
Salim
To convert temperatures in degrees Celsius to Fahrenheit, multiply by 1.8 (or 9/5) and add 32.
Salim
what is d final ans for Fahrenheit and Celsius
Celine
it said what is temperature change in Fahrenheit and Celsius
Celine
the 15 is already in Celsius
Salim
So the final answer for Fahrenheit is 59
Salim
what is d final ans for Fahrenheit and Celsius
Celine
what are the effects of placing a dielectric between the plates of a capacitor
Bundi Reply
increase the capacitance.
Jorge
besides increasing the capacitance, is there any?
Bundi
mechanical stiffness and small size
Jorge
so as to increase the capacitance of a capacitor
Rahma
also to avoid diffusion of charges between the two plate since they are positive and negative.
Prince
The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is
Mukesh Reply
Properties of longitudinal waves
Sharoon Reply

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Source:  OpenStax, Siyavula textbooks: grade 10 physical science [caps]. OpenStax CNX. Sep 30, 2011 Download for free at http://cnx.org/content/col11305/1.7
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