3.6 Flashcards
what did the theory of EM Waves predict
the existence of em waves beyond the visible spectrum
what did the discovery of X-rays and radio waves prove
proved to scientists that there was light beyond the visible spectrum
what does the dual nature of light mean
that light can behave as a wave or a particle depending on circumstance
when is wave like nature of light observed
when diffraction of light takes place
an example of diffraction
the light passes through a narrow slit.
the light emerging from the split spreads out in the same way as water waves spread out after passing through a gap
what causes a greater amount of diffraction
a longer wave length or a narrower gap
when is the particle like nature observed
in the photoelectric effect
when light is directed at a metal surface an electron absorbs a photon of frequency f. the kinetic energy of the electron is increased fro negligible to hf
the electron can escape from it if the energy it gains from the photon exceeds the work function
what is evidence the electrons have a particle like nature
electrons in a beam can be deflected by a magnetic field
who first considered that particles may also have a wavelike nature
Louis de Broglie (de Broglie hypothesis)
what was the de Broglie hypothesis
matter particles have a dual wave particle nature
the wavelike behaviour of a matter particle is characterised by a wavelength (de Broglie wavelength) lambda which is related to. the momentum
de Broglie wavelength equation
lambda = h/p. p =momentum
or
lambda = h/mv. mv also equal momentum as mass x velocity
how can the de Broglie wavelength of a particle be changed
by changing the velocity of the particle
when was the wavelike nature of an electron found
three years after de broglies hypothesis as it demonstrated that a beam of electrons could be diffracted
what later confirmed the de Broglie theory
further experimental evidence using different types of particles
