Today: Electromagnetic Radiation; Light & Sources of Light; Atomic spectra Optical tweezers study of RNA polymerase Steve Block Lab, Stanford

Optical tweezers study of RNA polymerase

Exam 1 Results

Electromagnetic radiation / wave Carries energy Has momentum (oomph) (but does NOT have mass) In a vacuum travels at “light speed” (duh?) Behaves like particle AND wave (what the???) Oscillating Electric and Magnetic “Field”

Carries energy

Has momentum (oomph) (but does NOT have mass)

In a vacuum travels at “light speed” (duh?)

Behaves like particle AND wave (what the???)

Oscillating Electric and Magnetic “Field”

Electromagnetic spectrum Carries energy Has momentum (oomph) (but does NOT have mass) In a vacuum travels at “light speed” (duh?) Behaves like particle AND wave (what the???) Oscillating Electric and Magnetic “Field” Wavelength (meters) Frequency (Hz) Temperature required to glow this color

Carries energy

Has momentum (oomph) (but does NOT have mass)

In a vacuum travels at “light speed” (duh?)

Behaves like particle AND wave (what the???)

Oscillating Electric and Magnetic “Field”

Electromagnetic radiation / wave More like waves More like particles Wavelength (meters) Frequency (Hz) Temperature required to glow this color

Clicker Question—Electromagnetic Waves, Frequency Which of these EM waves has the highest frequency Radiowave Ultraviolet Visible red light Microwave

Which of these EM waves has the highest frequency

Radiowave

Ultraviolet

Visible red light

Microwave

Clicker Question—Electromagnetic Waves, Frequency Which of these EM waves has the highest frequency Radiowave Ultraviolet Visible red light Microwave

Which of these EM waves has the highest frequency

Radiowave

Ultraviolet

Visible red light

Microwave

What are sources of electromagnetic radiation (EM)? Sunshine … fusion / atoms? Core of Earth (Earth’s magnetism) Microwave (oven/sure) …. Electrons Cell phones (microwaves) … electrons are oscillating Radio waves … antennaes … metal electricity / electrons Gamma rays … from pulsars (could be proton / neutrons) Infrared and light waves from an explosion (lots of different electron thing)

You are always basking in a glow of EM radiation! EM Waves are everywhere, always Even in the “dark” or in “space” Because you are at 310 Kelvin (98.6 degrees), you emit radiation yourself!

EM Waves are everywhere, always

Even in the “dark” or in “space”

Because you are at 310 Kelvin (98.6 degrees),

you emit radiation yourself!

Cosmic Background Microwave Radiation Universe Opaque Universe Transparent

Visible light is a small portion of the EM spectrum But of course, the most “colorful”! Key concept: Energy of photon is proportional to frequency E = h * f

Models of the atom evolved quickly in the early 1900’s Electron “Shells” Figure 11.6 in texbook http://www.csmate.colostate.edu/cltw/cohortpages/viney/atom2.jpg Electron clouds http://www.youtube.com/watch?v=fKYso97eJs4&feature=related Plum Pudding “ Solar System” model

Atomic spectra http://www.walter-fendt.de/ph11e/bohrh.htm (Standing waves and resonance for Bohr model) http://www.lon-capa.org/~mmp/kap29/Bohr/app.htm http://www.youtube.com/watch?v=l4yg4HTm3uk Spectrum of the stars

A) Each type of gas has a different molecular weight, which causes the nucleus to have different possible energy levels B) Each type of gas has a different orbital structure, which leads to different possible electron energy differences in the emission lines What causes the emission lines of various gases to differ in color?

A) Each type of gas has a different molecular weight, which causes the nucleus to have different possible energy levels

B) Each type of gas has a different orbital structure, which leads to different possible electron energy differences in the emission lines

Laser light can be used to create a real-life “tractor beam” Fictional Tractor Beam Steve Block Lab, Stanford “ Laser Tweezers” for biophysics experiments

“ Laser Tweezers” or “Optical tweezers” have become incredibly powerful tools for biophysics Optical tweezers I built at Cornell (M. Wang lab w/ Richard Yeh)

Here are some actual videos of optical tweezers in action Sorting colored microspheres http://www.ppo.dk/Research-OT.html Fiber optical trap, http://members.yline.com/~tweezers/gallery.htm Kinesin Molecular Motor http://www.scripps.edu/milligan/research/movies/kinesin_mpg.html Steve Block Lab, Stanford

Clicker Question—Light Hopefully you know that light carries energy . But does light carry momentum? Yes, always Sometimes No! Light does NOT have mass! Edned lecture here

Hopefully you know that light carries energy . But does light carry momentum?

Yes, always

Sometimes

No! Light does NOT have mass!