Electromagnetic Waves

• What are electromagnetic waves defined as?

  Transverse waves that transfer energy from the source to an absorber
• What are the shared properties of all electromagnetic waves?

  • All are transverse
  • Can travel through a vacuum
  • Travel at the same speed in a vacuum
• How many types of electromagnetic waves are there?

  Seven types
• How is the electromagnetic spectrum arranged?

  • Based on wavelengths or frequencies
  • From longest wavelength (lowest frequency) to shortest wavelength (highest frequency)

  
• What part of the electromagnetic spectrum is visible light?

  Visible light is a small part of the larger electromagnetic spectrum

  
• What happens to the energy of radiation as frequency increases?

  The energy of the radiation increases
• What are the characteristics of radiation with higher energy?

  • Highly ionising
  • Harmful to cells and tissues, causing cancer (e.g., UV, X-rays, Gamma rays)
• What are the characteristics of radiation with lower energy?

  • Useful for communications
  • Less harmful to humans
• What percentage of the electromagnetic spectrum does visible light occupy?

  0.0035%
• Which animals can perceive wavelengths beyond visible light?

  Birds, bees, and certain fish
• What are the colors of the visible spectrum in order?

  • Red (longest wavelength, lowest frequency)
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet (shortest wavelength, highest frequency)
• What mnemonic can help remember the colors of the visible spectrum?

  “Roy G. Biv” or “Richard Of York Gave Battle In Vain”
• How does the electromagnetic spectrum relate to wavelength?

  • Arranged in order of decreasing wavelength
  • Radios have long wavelengths; gamma rays have short wavelengths

  
• How do electromagnetic waves transfer energy?

  They carry energy from one point to another
• What type of EM waves carry higher energy?

  Waves with shorter wavelengths, such as UV, X-rays, and gamma rays
• How do microwaves transfer energy?

  • Water molecules absorb certain wavelengths of microwave radiation
  • Microwave ovens transfer energy to the thermal store of food

  
• What types of EM radiation does the Sun emit?

  • Visible light (allows creatures to see)
  • Infrared (heats the Earth)
  • Ultraviolet (causes suntans and sunburn)

  
• What happens to EM waves when they move from one medium to another?

  • They can be transmitted, absorbed, reflected, or refracted
  • Interaction depends on wavelength and the material
• What does glass do to visible light?

  Glass transmits and/or refracts visible light
• What happens to EM waves when they enter a denser medium?

  They slow down and bend towards the normal
• What is the effect of different speeds of EM waves in different substances?

  • Causes refraction
  • Different parts of the wave enter the medium at different times
• What is the normal line in refraction diagrams?

  A hypothetical line perpendicular to the surface of the boundary
• How does light behave when passing from less dense to more dense media?

  • Bends towards the normal
  • Slows down
• How does light behave when passing from more dense to less dense media?

  • Bends away from the normal
  • Speeds up
• What properties change during refraction?

  Speed and wavelength change; frequency remains constant
• What is the aim of the infrared radiation experiment?

  • Investigate how the amount of infrared radiation absorbed or radiated depends on surface nature
• What are the variables in the infrared radiation experiment?

  • Independent variable: Colour
  • Dependent variable: Temperature
  • Control variables: Identical flasks, same amounts of hot water, same starting temperature, same time interval
• What equipment is used in the infrared radiation experiment?

  • Thermometer (resolution: 1°C)
  • Stopwatch (resolution: 0.01 s)
• What factors affect the intensity of emitted thermal radiation?

  • Temperature of the body
  • Surface area of the body
  • Colour of the surface
• What are systematic errors in the infrared radiation experiment?

  • Ensure starting temperature is the same
  • Best to do in pairs for coordination
  • Use a data logger for accuracy
• What are random errors in the infrared radiation experiment?

  • Ensure thermometer hole isn’t too big
  • Take repeated readings
  • Read thermometer values at eye level
• What safety considerations should be taken during the infrared radiation experiment?

  • Keep water away from electrical equipment
  • Do not touch hot water directly
  • Run burns under cold water for at least 5 minutes
  • Avoid overfilling the kettle
  • Conduct experiment while standing
• What should you avoid to prevent parallax error?

  Avoid parallax error
• What are the safety considerations when working with electrical equipment and water?

  • Keep water away from all electrical equipment
  • Do not touch hot water directly
  • Run burns under cold running water for at least 5 minutes
  • Do not overfill the kettle
  • Keep equipment in the middle of the desk
  • Carry out experiments while standing
• What is the consequence of not controlling variables in an investigation?

  We cannot determine if the effect measured is due to the independent variable
• Why is it important to control the surface area in an energy transfer experiment?

  To ensure the surface area of each container is the same
• What should be the initial temperature of each flask in an energy transfer experiment?

  It should be the same for all flasks
• What are the two ways atoms can interact with electromagnetic (EM) waves?

  Atoms can absorb or emit EM waves
• What happens when an EM wave hits an atom?

  It can be absorbed by an electron, giving it energy
• What occurs when an electron moves down to a lower energy level?

  It emits an EM wave in the process