The speed of sound in air is approximately equal to 340 ms'

1
The speed of sound in air is approximately equal
to 340 m/s.
2
Anatomy of a wave
crest
crest
wavelength
amplitude
trough
3
One wave per second indicates a frequency of
frequency
given a wavelength
4
What happens to the frequency of a wave when its
wavelength is increased?

• There is an inverse relationship between
  wavelength and frequency
• If the frequency is doubled, the wavelength is
  cut in half

5
Doppler effect

• The Doppler effect is the change in frequency of
  a wave caused by the relative motion of the wave
  emitter and receiver.

6
The car engine is emitting the sound waves and is
the wave emitter

• Your ear is the wave receiver

7
The Doppler effect indicates that the universe is
expanding

• Hubble picture of the Whirlpool galaxy on the
  left and the Eagle Nebula on the right

8
Early police radar guns relied on the Doppler
effect

• Knowing the original frequency, the speed of
  light and the change in frequency, the computer
  solved for the speed of the car.

9
Modern Radar gun
position
time

• The slope of the position versus time graph
  yields the velocity of the car.

10
Light travels as waves

• The speed of light in a vacuum is 3 x 108 m/s
• Nothing travels faster

11
Sound travels as waves

• The speed of sound in air is approximately 340
  m/s
• The speed of light in air is approximately 3 x
  108 m/s

12
Light is fast, but it is not infinitely fast

• Light can travel a distance equal to 7 times
  around the Earth in 1 second

13
James Maxwell calculated that the speed of an
electric field magnetic field combo is 3 x 108 m/s

• As the two fields exchange energy they radiate
  from their source at the speed of light

14
Electromagnetic radiation-light
15
A ray of light
C

• Different types of light have different
  frequencies and therefore different amounts of
  energy

16
Some types of light
Radio waves
Infrared
visible
X-ray
gamma ray
Microwaves
Frequency increasing toward the right
Energy of the photons is increasing toward the
right
Wavelength is decreasing toward the right

• Visible light is only a small part of the
  electromagnetic spectrum

17
Although light travels the fastest through a
vacuum, there are lots of other media that light
can travel through

• Light travels very well through air, water and
  glass.

18
Radio stations transmit light

• At a radio station, sound is converted to
  electrical signals and these are then converted
  to light.
• A radio converts the light that was transmitted
  by the radio station back to electrical signals
  and then to sound.

19
Photon- a bundle of light energy
C

• A combination of electric and magnetic fields
  exchanging energy

20
Visible white light is a combination of all of
the colors or the rainbow
Red
Orange
Green
Blue
Yellow
Indigo
Violet

• When ROYGBIV are combined, the results are white
  light

21
Range of white light wavelengths
380 nm
770 nm
Orange
Green
Blue
Indigo
Violet
Red
Yellow

• The different colors represent the different
  frequencies and wavelengths of white light

22
Nanometer nm

• 1 nm is 1 millionth of a millimeter

23
The limit of resolution is determined by
wavelength

• We cant see things that are smaller than the
  wavelength

24
How do we see things?

• Visible light either comes directly to our eyes
  or reflects off objects and then comes to our
  eyes.
• Our brain then creates an image.

25
Louis de Broglie hypothesized that fast moving
electrons would have a wavelength that is much
smaller than that of light.

• An electron moving at 10 the speed of light
  would have a wavelength of .1nm, thats the size
  of a hydrogen atom

26
The smaller the wavelength, the larger the
photons energy will be
27
Ultraviolet light is not visible to the human eye.

• Its photons have enough energy to kill cells

28
Ultraviolet photons are absorbed by the electrons
in glass and therefore do not pass through glass
29
Refraction is the bending of a wave as it passes
from one medium to the next
incident ray
reflected ray
refracted ray