Science..unit 2!!

• Sound waves


  Mechanical longitudinal waves
• Sound waves


  • They need a medium (as air) to propagate through
  • The medium particles vibrate in the same direction of wave propagation forming compressions and rarefactions
• Sound waves propagate through media as spheres of compressions and rarefactions, whose centre is the source of sound
• Sound


  An external factor (or stimulus) that affects the ear causing the sense of hearing
• We hear sound from all directions that surround the sound source
• Sound travels through air at a velocity 340 m/sec
• Calculating sound wave velocity


  Frequency x Wavelength
• Sound waves produced from a vibrating tuning fork


  • Frequency 512 cycles/sec
  • Wavelength 60 cm
• Musical tones


  Tones of uniform frequency and comfortable to be heard
• Musical tones


  • Violin
  • Piano
  • Reed pipe
• Noises


  Sounds of non-uniform frequency and uncomfortable to be heard
• Noises


  • Drill
  • Loudspeakers
  • Horns of cars
• Sound pitch


  The property by which the ears can distinguish between harsh and sharp voices
• High pitched sound is sharp (soft), low pitched sound is harsh (rough)
• Sound pitch


  Increases by increasing the frequency and vice versa
• Sharp tones have high frequency, harsh tones have low frequency
• Length of air column

  As it increases, the sound frequency decreases, so the harshness of sound increases
• Length of air column

  As it decreases, the sound frequency increases, so the sharpness of sound increases
• Calculating frequency of a musical tone using Savart's wheel

  Frequency = No. of cycles x No. of gear teeth / Time in seconds
• Calculating number of gear teeth in Savart's wheel

  No. of gear teeth (n) = Frequency (F) x 60 / No. of cycles (d)
• Calculating time taken by Savart's wheel to make 600 cycles

  Time (t) = 600 x No. of gear teeth (n) / Frequency (F)
• Sound intensity


  The property by which the ears can distinguish between strong or weak sounds
• Noise intensity


  Measured in Decibel
• Factors affecting sound intensity

  • Distance between ear and sound source
  • Amplitude of vibration of sound source
  • Area of vibrating surface
  • Medium density
  • Wind direction
• Sound intensity


  Inversely proportional to the square of the distance between the point and the sound source
• Sound intensity


  Directly proportional to the square of the amplitude of the vibration of the sound source
• Sound intensity


  Directly proportional to the area of the vibrating surface
• Sound intensity


  Directly proportional to the density of the medium
• Sound intensity


  Decreases when the direction of sound propagation is opposite to the wind direction
• Sound quality (type)


  The property by which the human ear can distinguish between different sounds according to the nature of the source
• Fundamental (basic) tone


  A pure simple tone
• Harmonic tones


  Tones that accompany the fundamental tone but are higher in pitch and lower in intensity, and differ from one instrument to another
• Infrasonic waves


  Sound waves of frequencies lower than 20 Hz
• Ultrasonic waves


  Sound waves of frequencies higher than 20 KHz (20000 Hz)
• Real life applications of ultrasonic waves

  • Breaking down kidney and ureter stones
  • Diagnosis of male prostate gland tumors
  • Discovering malignant tumors
  • Sterilization of food, water and milk
  • Sonar
  • Milk sterilizer
• Light


  An external factor (or stimulus) that affects the eye causing the sense of vision
• Light waves


  • They are electromagnetic transverse waves
  • They propagate through vacuum
  • The medium particles vibrate perpendicular to the direction of the wave propagation forming crests and troughs
• Speed of light


  The distance covered by light in one second
• Electromagnetic spectrum


  • Gamma-ray
  • X-ray
  • Ultraviolet
  • Visible light
  • Red
  • Violet
• Analysis (or splitting) of white light

  1. Visible light is one of the components of electromagnetic spectrum of wavelength ranges between 380 : 700 nanometre

  2. It is the splitting of white light into seven colours called spectrum colours

  3. Lowest deviation is the closest to the prism apex, lowest frequency, longest wavelength

  4. Deviation increases, frequency increases, wavelength decreases

  5. Highest deviation is the closest to the prism base, highest frequency, shortest wavelength