How fast is that?

       299 792 458 m / s or 3.00*10

8 m/s

Around the Earth 8 times in one second 1.5 seconds to the Moon 4 minutes to Mars 8 minutes to the Sun 30 minutes to Jupiter 4.24 years to the NEAREST star

Light Year

   One light-year (ly) is the distance that light travels in a year 9.46 × 10 15 meters About 6 trillion miles

Yes, that’s FAST!

Solar System Travel

Time to Speed Time to Jupiter

Freeway Speed Jetliner Speed 75 mph 500 mph 600 yrs 90 yrs Concorde Speed (Mach 2) 1350 mph 33 yrs Spacecraft Speed (Voyager) 40,000 mph 1.5 yrs

α Cen

38 million yrs 6 million yrs 2 million yrs 70,000 * yrs

Way Big

Our Milky Way Galaxy is only 100 000 light years across or about 600 000 000 000 000 000 miles or 6 x 10 17 miles or 9.5 x 10 17 km or 9.5 x 10 20 meters or 950 000 000 000 000 000 000 meters

What is light?

  Light is an electromagnetic wave Oscillating electric and magnetic fields  Oscillations are in phase   In phase--When Electric field is increasing, Magnetic field is increasing. When E field is decreasing, Magnetic field is decreasing

More on EM wave

  Electric and magnetic fields are perpendicular to each other and the direction of travel Transverse wave

You might have heard…

  …that light acts as both particle and wave It does, but for most of this class, light is a wave.

White Light

  White light is made of a range of frequencies or colors Can be separated into six elementary colors of the visible spectrum  Spectrum—The distribution of wavelengths and frequencies

Visible light

  Visible Spectrum—Red, Orange, Yellow, Green, Blue, and Violet.  Indigo was demoted :<( Roy G. Bv

EM Spectrum

Speed of EM waves

     All EM waves travel at 3.00*10 8 m/s Energy of EM waves depends on frequency.

 Gamma rays=HIGH energy, radio waves=low energy Speed of the wave depends only on the medium - constant in a constant medium Water 75% Glass 67% Diamond 41% Nothing can travel faster than light in a vacuum

Measuring speed of light

  Galileo was one of the first to try  Tried to determine time it took light to travel 1.5 km. Would he be able to measure the speed?

Now, error is less than .0001%

Wave Speed Equation:

 

c=f λ

Speed of light=frequency x wavelength

Example

   Red light has a wavelength of 750nm. What is the frequency? c=3.00*10 8 m/s First, 750nm = 750*10 -9 m = 7.5*10 -7 m Plug into c=f λ   (3.00*10 8 m/s) / (7.5*10 -7 m) = f f=4.0*10 14 Hz