Survey of the Universe

Tom Burbinetburbine@mtholyoke.edu

Prospective Astronomy Majors Lunch

Meet the faculty, learn about the Mars Rover, and enjoy a delicious lunch.

Monday, March 4th

12:15-1:10pmKendade 303

HW# 3

• Due March 6

Characteristics of waves• velocity = wavelength x frequency• Wavelength = distance• Frequency = cycles per second = hertz

For light

• c = wavelength x frequency• In a vacuum, speed of light stays the same• So if wavelength goes up• Frequency does down• f = frequency• λ = wavelength• c = λ x f

Calculations

• c = λ x f• So if the wavelength is 1 x 10-12 m• 3 x 108 m/s = 1 x 10-12 m * f• f = 3 x 108 m/s/1 x 10-12 m • f = 3 x 1020 s-1 = 3 x 1020 Hz

Calculations

• c = λ x f• So if the frequency is 1 x 1015 Hz• 3 x 108 m/s = λ * 1 x 1015 Hz • λ = 3 x 108 m/s/1 x 1015 Hz • λ = 3 x 10-7 m

Energy of light

• Energy is directly proportional to the frequency• E = h * f• h = Planck’s constant = 6.626 x 10-34 J*s• since f = c/λ• Energy is inversely proportional to the wavelength• E = hc/λ

Calculations

• What is the energy of a radio wave with a frequency of 1 x 107 Hz?

• E = h * f• h = Planck’s constant = 6.626 x 10-34 J*s• E = 6.626 x 10-34 J*s * 1 x 107

• E = 6.626 x 10-27 J

Calculations

• What is the energy of a gamma ray photon with wavelength of 1 x 10-15 m

• E = hc/λ• h = Planck’s constant = 6.626 x 10-34 J*s• E = 6.626 x 10-34 J*s * 3 x 108 m/s / 1 x 10-15 m• E = 1.99 x 10-10 J

Higher the frequency, Higher the energy of the photonHigher the wavelength, Lower the energy of the photon

redviolet

VIBGYOR

ROYGBIV

• ROYGBIV • Red – long wavelength• Violet – short wavelength

http://www.arpansa.gov.au/images/basics/emr.jpg

Any Questions?