W2: EM waves

Question 1

How do all EM waves differ from each other?

Answer 1

wavelength: long wavelengths (radio waves) or short wavelengths (gamma rays)
frequency: low frequency (radio waves) or high frequency (gamma rays)
energy: higher frequency = higher energy, lower frequency = lower energy

Question 2

What do EM waves have in common?

Answer 2

• consists of electric and magnetic fields
• travels at a constant speed of light in a vacuum, 3.0 x 10^5 km/s (1.86 x 10^5mi/s)
• travel through vacuum
• travels as waves enclosed in a discrete packets called photons

Question 3

Arrange all types of EM waves in order or increasing energy on the axis below.

Answer 3

(lowest energy/
long wavelength)
- Radio Waves
- Microwaves
-Infrared
- Visible Light
- Ultra violet
- Xrays
- Gamma rays
(highest energy/
short wavelength)

Question 4

How does sound and light differ from each other?

Answer 4

sound

nature: mechanical wave that requires a medium
for transmission
speed: travel slower
sensory perception: perceived by ears as vibration sin the air

light

nature: electromagnetic wave that can travel through a vacuum
speed: travel faster 3.0 x 10^5 km/s (1.86 x 10^5mi/s)
sensory perception: perceived by our eyes as electromagnetic radiation, allowing us to see objects and colours

Question 5

Explain the term: Doppler Effect

Answer 5

change in wave frequency during the relative motion between a wave source and its observer.

Question 6

2 examples of the Doppler Effect used in real Astronomy today.

Answer 6

• redshift in galaxies
• stellar wobble

Question 7

2 examples of the Doppler Effect seen in everyday life (on Earth)

Answer 7

• sirens on emergency vehicles
• train horn: approaching, high pitch. moves a way, lower pitch

Question 8

Radio waves, example of:
- natural EM wave sources from space (cosmic)
- natural EM wave sources from space (cosmic)

Answer 8

• pulsars: rapidly rotating
  neutrons that emit beams
  of electromagnetic radiation
• wifi and bluetooth:
  use radio waves to enable
  devices to connect to the
  internet and communicate

Question 9

Ultra violet, example of:
- natural EM wave sources from space (cosmic)
- natural EM wave sources from space (cosmic)

Answer 9

• sun: emits a broad
  spectrum of UV radiation
• tanning beds: emit UV-A and
  UV-B radiation to induce
  tanning of the skin