Dawn of Modern Physics Flashcards
What is a reference frame?
A coordinate system in which an experimenter makes position and time measurements of a physical events.
What is initial and non initial reference frames?
One in which an object subjected to no forces moves in a straight line with constant speed is IRF and an accelerating frame of reference is called NIRF.
What is thermal radiation?
Electromagnetic radiation emitted by objects because of their temperature.
What is a black body?
A body at a constant temperature absorbs and re-emits all the electromagnetic radiation that falls on it.
What are radiations emitted by black body are called?
Black body radiations.
What is constant value for Wien’s displacement law?
0.2898 x 10^-2 mk.
What is constant value for Stephen’s law?
5.67 x 10^-8 WmK.
What are 2 postulates of planck’s theory?
Atoms/molecules cant emit/absorb energy in all possible ways but an oscillating atom/molecule can emit/absorb energy ONLY in discrete bundles (photon or quanta).
Atoms/molecules will emit/absorb energy only when it changes states. 1 quantum state means no energy emitted/absorbed.
Who discovered Photoelectric effect and when?
Heinrich Hertz in 1887.
What is photoelectric effect?
When light hits the metal surface, electrons are emitted.
Is energy of electromagnetic radiation continuously distributed over the wavefront?
No, in localized bundles of quanta or photons.
Describe compton effect.
The scattering of high frequency photon (x ray) with less frequency by a stationary electron.
What is the value of compton wavelength?
2.43 x 10^-12 m.
What is pair production?
The creation of an elementary particle and its antiparticle, usually when a photon interacts with nucleus resulting in an electron and a positron.
Can a photon create an electron alone in pair production?
No. Law of conservation of charge would be violated.
Is presence of nucleus required in pair production?
Yes. To conserve law of conservation of momentum.
Photon energy required for pair production?
1.02 MeV energy photon.
Describe Pair annihilation.
When an electron and photon collide, 2 gamma ray photons are produced.
Which experiment showed wave like nature of an electron?
The Davisson-Germer experiment.
What is an electron microscope?
Type of microscope which uses an electron beam with its wave like properties to illuminate a specimen and produce a magnified image.
State uncertainty principle.
The more precisely the position is determined, the less precisely the momentum is known and vice versa.
