Explain the formation of interference patterns
- laser light made up of electromagnetic waves
- as the waves pass through mesh > diffract
- when light reaches screen > interference pattern
- when light from different waves meet the screen in phase with one another > constructive interference (resulting in maxima)
- light arrives in phase with path difference n(wavelength), where n = 1,2 etc
Assess the evidence for Newton’s theory of light
- very little evidence to support
- newton’s theory state that light consists of small solid particles with intrinsic properties such as shape and sides
- could accurately predict reflection and refraction of light, and dispersion into the colours
- no empirical evidence that supported the wave model, and he was contradicted through Young’s double slit
Assess the evidence for Huygen’s theory of light
- consisted of wave model of light (where wavelets propagate from individual spreading out centres along the wavefront)
- Huygen’s theory was clearly supported through empirical evidence
- Young’s double slit experiment, demonstrating diffraction and interference patterns provided strong evidence
- Foucault verified Huygen model by showing that light travels slower in denser material
Assess Maxwell’s contribution to the classical theory of electromagnetism
- vitally important to classical theory (3 predictions)
- light is an em wave, with self-propagating electric and magnetic fields
- light is only one part of spectrum
- the speed of electromagnetic waves is c
- Maxwell was the foundation of electromagnetism
Explain how the spectra of a star is produced, and how it can be used to show the star’s composition
- continuous spectrum is emitted from the core of the star
- travels outwards through the photosphere
- photons with energies that correspond to the atomic energy level transitions of the gases that make up the photosphere are absorbed
- photons of these energies are missing from the emission spectra of the star on earth
- each element in the star will give rise to a unique series of lines which enables elements present in the star to be determined (chem comp)
- the abundance of these elements are measured through the intensities of the spectral lines
characteristics of stars found from its spectra
surface temp
- determined through Wein’s Law, where wavelength max is determined from the stars spectrum.
- longer wavelengths > cooler temp
- shorter wavelengths > warmer temp
chemical comp
- found by comparing the emission spectra of known elements, with the absorption spectra of a star
- the absorption levels ate present due to the atomic energy level transitions of the atoms in the photosphere
- shared bonds indicate the elements presence
translational velocity
- obtained through red or blue shift
- red-shifted (longer wavelength) it is moving away
- blue-shifted (shorter wavelength) it is moving towards
- the larger the shift, the faster it’s moving
rotational velocity
- determined through the width of the absorption bands
- faster it is rotating, the wider the absorption bands are
density layers
- obtained through the spectra
- wider absorption pattern for more dense (as a more dense star has more collisions)
- this is called collisional broadening
Explain strategies to improve transformer efficiency
- Eddy currents (resistive heating effects)
laminate to have smaller or prevent eddy currents - Incomplete flux linkage between primary and secondary
solid iron core
