Physics CP04 Waves

• What does the speed of a wave depend on?

  The medium through which it travels
• How can you calculate the speed of a wave?

  Speed = wavelength × frequency
• What is the difference between transverse and longitudinal waves?

  Transverse waves oscillate perpendicular to the direction of travel, while longitudinal waves oscillate parallel.
• Calculate the wavelength of a wave that travels at a speed of 200 m/s and has a frequency of 50 Hz.

  $\text{Wavelength} =$$\frac{\text{Speed}}{\text{Frequency}} =$$\frac{200 \text{ m/s}}{50 \text{ Hz}} =$$4 \text{ m}$
• Calculate the speed of a wave that has a wavelength of 100 m and a frequency of 2 Hz.

  $\text{Speed} =$$\text{Wavelength} \times \text{Frequency} =$$100 \text{ m} \times 2 \text{ Hz} =$$200 \text{ m/s}$
• How do you measure the speed of water waves?

  By measuring the distance between crests and the time taken for a certain number of waves to pass.
• If each wave has a wavelength of 10 cm and the time taken for 5 waves to pass is 15 seconds, what is the speed of the waves?

  $\text{Speed} =$$\frac{\text{Distance}}{\text{Time}} =$$\frac{5 \times 10 \text{ cm}}{15 \text{ s}} =$$\frac{50 \text{ cm}}{15 \text{ s}} \approx 3.33 \text{ cm/s}$
• What is the relationship between the energy transferred by a wave and its amplitude and frequency?

  Energy is related to both amplitude and frequency; stronger waves have larger amplitude and higher frequency.
• Calculate the speed of a tsunami with a wavelength of 200 km and a frequency of 0.015 Hz.

  $\text{Speed} =$$\text{Wavelength} \times \text{Frequency} =$$200,000 \text{ m} \times 0.015 \text{ Hz} =$$3000 \text{ m/s}$
• What factors affect the speed of a wave?

  The medium, temperature, density, and humidity.
• Why is it more difficult to measure the speed of a water wave than a sound wave?

  Water waves are influenced by surface tension and depth, making them less consistent.
• What is the speed of sound in air?

  Approximately 340 m/s
• If the sound from a thunderstorm takes 4 seconds to reach you, what is the approximate distance of the thunderstorm?

  $\text{Distance} =$$\text{Speed} \times \text{Time} =$$340 \text{ m/s} \times 4 \text{ s} =$$1360 \text{ m}$
• What is the speed of electromagnetic waves?

  The speed of light, approximately $3 \times 10^8 \text{ m/s}$
• What factors affect the speed of water waves?

  The depth of water, wavelength, and surface tension.
• Calculate the frequency of a wave with a speed of 5 m/s and a wavelength of 10 m.

  $\text{Frequency} =$$\frac{\text{Speed}}{\text{Wavelength}} =$$\frac{5 \text{ m/s}}{10 \text{ m}} =$$0.5 \text{ Hz}$
• What is refraction?

  The change in direction of light when it passes from one transparent material to another.
• What factors affect the amount of refraction of light?

  The angle of incidence and the refractive indices of the materials.
• How does the refractive index of air compare to that of water?

  Air has a refractive index of approximately 1, while water has a refractive index of approximately 1.33.
• How does refraction allow us to see objects underwater?

  Light rays bend when they pass from water to air, allowing us to see objects that are submerged.
• How can a prism separate white light into its constituent colors?

  By refracting different wavelengths of light at different angles.
• What is the definition of refractive index?

  A measure of how much a material can bend light.
• What is the normal in optics?

  An imaginary line perpendicular to the surface separating two media.
• What is total internal reflection?

  The complete reflection of light at the boundary between two media when light passes from a denser to a less dense medium.
• How is total internal reflection used in optical fibers?

  It allows light to be transmitted through the fiber without escaping.
• How is total internal reflection used in prisms?

  It allows prisms to reflect light at specific angles to create images.
• What is the relationship between the speed of light and the refractive index of a material?

  The speed of light decreases as the refractive index increases.
• Calculate the angle of refraction when a light ray hits glass at an angle of 30° with a refractive index of 1.5.

  $\text{Using Snell's Law: } n_1 \sin(\theta_1) =$$n_2 \sin(\theta_2) \Rightarrow 1 \cdot \sin(30°) =$$1.5 \cdot \sin(\theta_2) \Rightarrow \sin(\theta_2) =$$\frac{1 \cdot 0.5}{1.5} \Rightarrow \theta_2 \approx 19.47°$
• What are the steps to investigate the relationship between the mass of a load and the speed of a crab carriage?

  1. Set up the apparatus on a level surface.
  2. Measure a distance of 2m.
  3. Place a weight on the crab carriage.
  4. Release the carriage and start the stopwatch.
  5. Stop the stopwatch when the carriage travels 2m.
  6. Record the time and repeat for accuracy.
  7. Calculate speed using speed = distance/time.
• What are the possible sources of error in the crab carriage experiment?

  • Inconsistent starting position
  • Friction on the surface
  • Timing inaccuracies
  • Variability in weight placement
• How could you improve the accuracy of the crab carriage experiment results?

  • Use a more precise stopwatch
  • Ensure a consistent release method
  • Conduct more trials for averaging
  • Minimize friction on the surface
• What would happen to the speed of the crab carriage if a much larger mass is used?

  • The speed may decrease due to increased friction and inertia.
  • The acceleration may be affected by the added weight.
• What is the relationship between the speed of waves and their properties?

  • Speed is influenced by wavelength, frequency, and the medium.
  • Higher frequency and longer wavelength generally increase speed.
• What are the characteristics of transverse and longitudinal waves?

  • Transverse waves: oscillate perpendicular to direction of travel.
  • Longitudinal waves: oscillate parallel to direction of travel.
• What are the factors affecting the speed of sound?

  • Temperature of the air
  • Density of the air
  • Humidity of the air
• What is the significance of the refractive index in optics?

  • It measures how much light bends in a material.
  • Higher refractive index indicates greater bending of light.
• How do lenses utilize refraction?

  • Convex lenses focus light to a point.
  • Concave lenses spread light rays apart.
• What causes a mirage?

  • Refraction of light due to temperature differences in air.
  • Light bends upwards from cooler to warmer air.
• What is total internal reflection and its applications?

  • Complete reflection of light in denser to less dense medium.
  • Used in optical fibers and prisms for light transmission.
• What is the relationship between speed of light and refractive index?

  • Speed of light decreases as refractive index increases.
  • Higher refractive index means light travels slower in that medium.