# April 25 AP Physics.

## Presentation on theme: "April 25 AP Physics."— Presentation transcript:

April 25 AP Physics

In: A wire loop of radius 0.50 m lies so that an external magnetic field of magnitude 0.20 T is perpendicular to the loop. The field reverses its direction, and its magnitude changes to 0.30 T in 1.5 s. Find the magnitude of the average induced emf in the loop during this time.

Objective: To comprehend:
Quantum physics Photons, the photoelectric effect, Compton scattering Atomic physics Atomic energy levels Wave-particle duality

Atomic and Nuclear physics
Quantum physics Photons, the photoelectric effect, Compton scattering Atomic physics Atomic energy levels Wave-particle duality Nuclear physics: Nuclear reactions (including conservation of mass number and charge) Mass-energy equivalence

Attributed to William Thomson, 1st Baron Kelvin 1900
"There is nothing new to be discovered in physics now. All that remains is more and more precise measurement" Attributed to William Thomson, 1st Baron Kelvin 1900

Black body radiation and Max Planck’s quantum theory
German physicist Founder of quantum theory Nobel prize 1918

Photoelectric effect:

Einstein and the photoelectric effect
German born physicist 1905 “Miraculous Year” Special theory of relativity Mass/energy equivalency Photoelectric effect Brownian motion Nobel prize 1921

Graph for different metals

E = hf = pc Kmax = hf - Φ E = energy f = frequency K = kinetic energy
h= Planck’s constant 6.626 x j.s

Lithium has a work function of 2. 30 eV
Lithium has a work function of 2.30 eV. If 400-nm light is incident what is the maximum kinetic energy of the photoelectrons.

Arthur H. Compton American physicist
Discovered the phenomena called Compton scattering. Nobel prize 1927

Neils Bohr Danish Physicist
Explained atomic spectra with his model of the atom Nobel prize 1922

A stellar spectrum shows three absorption lines of hydrogen produced as electrons move from the n=2 state to higher energy levels (n=3, n=4, n=5) what are the wavelengths and colors of the three lines missing from the continuous spectrum?

Louis de Broglie French Physicist
Postulated that matter can behave as a waves Nobel prize 1929

If a wave can be a particle, can a particle be a wave?
λ=h p

If the wavelength of an electron is 5
If the wavelength of an electron is 5.00 × 10−7 m, how fast is it moving? (b) If the electron has a speed of 1.00 × 107 m/s, what is its wavelength?

Out: Why do you think that physicists in 1900 thought they had discovered everything?