November 22, 2013

Name of the Game:

ENERGYAnd also:

NOBEL PRIZES FOR PHYSICS

Energy, Wavelength, Frequency

• Long wavelength Low frequency Low energy

• Short wavelength High frequency High energy

Wave Model

• Studied: Black body radiation• Why do hot metals have a different color than

cold metals?

• Heat is energy• Color is visible light (EMR)

Max Planck (1918 – Nobel Prize)

Max Planck (1918 – Nobel Prize)

• Quantum:– A small packet of energy– Smallest amount of energy that

can be gained or lost by an atom

• Planck’s constant:h = 6.626 × 10-34 J· s

1858-1917

Energy is only emitted in “small packets”

Albert Einstein (Nobel Prize - 1921)

• Studied: Photoelectric effect

• In the photoelectric effect, electrons are emitted from matter when atoms absorb energy from electromagnetic radiation (EMR)

• Below a certain frequency of light, no electrons were emitted

Albert Einstein (Nobel Prize - 1921)• Light can behave as a wave

AND a particle

• “Dual wave-particle” nature of light

• Photon:– particle of electromagnetic

radiation– carries a quantum of energy– zero mass 1879-1955

The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation.

E = hE = Energy, in units of Joules (kgm2/s2)h = Planck’s constant (6.626 x 10-34 Js)v = frequency (Hz, s-1)

The big equation for Energy:

PRACTICE:

• What is the energy in Joules of a photon with a frequency of 4.0 × 1011 Hz? – E = hv = (6.626 x 10-34 Js)(4.0 x 1011Hz) = 2.65 x 10-22 J

• What is the frequency of a photon with an energy of 7.3 × 10-18 J?– E = hv 7.3 × 10-18 J = (6.626 x 10-34 Js)v (7.3 × 10-18 J)/(6.626 x 10-34 Js) = 1.1 x 1016 Hz

A few examples

• Gamma Radiation• Infrared• Ultraviolet• Microwaves

Gamma Radiation

• Space!• Nuclear decay• More on Tuesday…

Infrared: Remote Control

• “Below red”• How to see it on your camera phone:

http://www.wikihow.com/See-Infared-Light

Ultraviolet rays: The SunClick on the link to see how this experiment worked.

Ultraviolet Rays: BlackLight • What items will show up under a blacklight?• Why do some things phosphoresce under UV

light?• Fluorescent substances absorb the ultraviolet

light and then re-emit it almost instantaneously. Some energy gets lost in the process, so the emitted light has a longer wavelength than the absorbed radiation, which makes this light visible and causes the material to appear to 'glow'.

Microwave• Mental Floss: Discovery of (1:50)• Minute Physics: How it works

Your task…