6.2 - Electromagnetic Waves

• The electromagnetic spectrum is a continuous spectrum of all the possible wavelengths of electromagnetic waves.
• Label the wavelengths:

  A) -1

  B) 4

  C) 10 cm

  D) 1 cm

  E) 0.01 mm

  F) -2

  G) -5

  H) -7

  I) -8

  J) -10

  K) -15

  L) wavelength

  M) frequency

  
• Features of electromagnetic waves:

  • gamma rays - originates from atom's nucleus
  • X rays - ionising radiation, can cause mutations and lead to cancer
  • ultra violet - increases risk of cancer
  • Visible light - rage of wavelengths visible to humans
• Uses of electromagnetic waves (part 2):

  • Infrared - heaters and infrared cameras
  • microwaves - cooking food and communication
  • Radio waves - television and radio
• If an atom absorbs energy, some of its electrons move to higher energy levels within the atom. When the electron falls back down to its original energy level, an electromagnetic wave is produced.
• How are radio waves produced?

  Alternating currents are made up of oscillating charges (electrons). As they oscillate, they produce oscillating electric and magnetic fields. The frequency of radio waves produces will be equal to the frequency of the alternating current.

  The object in which charges oscillate to create the radio waves is called a transmitter
• How are radio waves recieved?

  • When transmitted radio waves reach a receiver, the radio waves are absorbed.
  • The energy carried by the waves is transferred to the kinetic energy stores of the electrons in the material of the receiver. Causing the electrons to oscillate and generates an alternating current.
  • This current has the same frequency as the radio wave that generated it.
• Fill in the blanks:

  A) oscillate

  B) ac

  C) transmitter

  D) reciever

  E) ac

  F) reciever

  G) absorbed

  H) oscillate

  
• Long-wave Radio:

  • wavelength 1-10 km
  • transmitted and received halfway round the world
  • can diffract (bend) around the curved surface of the earth
• Short-wave Radio:

  • wavelength 10-100 m
  • reflected between earth and ionosphere
  • Used in bluetooth to send data over short distances wirelessly
• What is an ionosphere?

  An electrically charged layer in the Earth's upper atmosphere
• Medium-wave Radio:

  They can reflect from the ionosphere depending on:

  • atmospheric conditions
  • time of day
• TV Signals and FM Radio:

  • wavelength 10cm - 10m
  • to get signal must be in direct sigh of transmitter
• Fill in the blanks:

  A) ionosphere

  B) transmitter

  C) diffract

  D) reflect

  E) ionosphere

  
• What are the uses of microwaves?

  Satellite communication and cooking
• What are the uses of infrared radiation?

  Infrared cameras, cooking and electric heaters.
• What is the use of visible light?

  Fibre optic cables
• What are the uses of ultraviolet radiation?

  Sun tanning lamps, security ink and energy efficient lamps
• Fill in the blanks about satellite communication:

  A) transmitter

  B) satellite

  C) microwaves

  
• Fill in the blanks about fibre optic cables:

  A) light

  B) fibre

  C) cladding

  D) glass

  
• What are the uses of X-Rays and Gamma Rays?

  Medical imaging and medical treatment
• What are the most dangerous types EM radiation?

  UV, X-Rays and gamma rays
• What are the dangers of EM radiation?

  sunburn, blindness, skin cancer.
• What is a radiation dose?

  A measure of the risk of harm from the body being exposed to radiation.
• What is radiation dose measured in?

  sieverts
• Radiation dose takes into account:

  • The total amount of radiation absorbed
  • How harmful the type of radiation is
  • The type of body tissue absorbing the radiation
• All objects are continually emitting infrared radiation, the hotter the object is, the more infrared radiation it emits.
• An object that is hotter than its surroundings emits more infrared radiation than it absorbs - so its temperature falls.
• Complete the diagram of the IR emission practical:

  A) Leslie cube

  B) heatproof

  C) infrared detector

  
• Complete the diagram about the IR absorption practical:

  A) ball bearing

  B) wax

  C) bunsen burner

  
• During the day, more radiation is absorbed than emitted, causing an increase in local temperature.
• Fill in the blanks:

  A) atmosphere

  B) surface

  C) clouds

  
• What is a perfect black body?

  An object that absorbs all of the electromagnetic radiation that hits it. No radiation is reflected or transmitted by its.
• As the temperature of an object increases, the intensity of every emitted wavelength increases.
• As the temperature of an object increases, the peak wavelength decreases.
• Fill in the blanks:

  A) decreases