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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

what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
what's microbiome?
john Reply
Microbiology is the scientific study of microorganisms
Ibra
the microorganisms in a particular environment (including the body or a part of the body).
Ibra
describe the bacterial cell
Akello
The biggest populations of microbes reside in the gut.other popular habitats include the skin genitals.The microbial cells and their genetic material ,the microbiome ,live with human from birth .
Zahreen
can agriculture be integrated into biology
David
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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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