Waves Section Flashcards
How can you increase the spacing between the maxima?
- Increase the separation of the sources
- Increase the wavelength of the waves
- Increase the distance between the sources and screen/detector
What is the amplitude of a wave?
The distace from the centre of a wave to the crest or trough.
What is meant by irradiance?
The power per unit area
What are the 4 differences in spectra produced by refraction (in a prism) and by a grating?
Prism Grating
One spectrum Many spectra
Produced by Refraction Produced by interference
Red light deviated least Red light deviated most
Spectrum is dim Spectrum is bright
Are all photons produced by energy level transitions visible?
No, some frequencies of photons may be in in the ultraviolet or X-ray frequency
What is destructive interference?
Destructive interference occurs when two waves meet at a point exactly 180O out of phase.
What is meant by diffraction?
Diffraction is the bending of waves round an object.
What is the ground state?
This is the energy level with the least energy. It is the most negative energy level.
What is the test for a wave?
If it can cause interference.
What do absorption lines in the Sun’s spectrum show?
Evidence for the composition of the upper atmosphere of the Sun.
What is a coherent source?
Waves that have a constant phase difference (and the same frequency, wavelength and velocity)
When will total internal reflection occur?
- Incident light must arrive at the boundary at an angle greater than the critical angle
- Occurs when light tries to pass from an optically dense material to a less dense material (e.g. from glass to air)
What is the critical angle?
The angle of incidence (within a material) that gives an angle of refraction of ninety degrees.
If white light is shone through a grating what does the interference pattern look like?
- The central order maximum will be white
- At every other maxima a spectrum will be produced
If a spectral line is bright - what des this tell you?
More electrons are making that energy level transition producing more photons of light with the same frequency.
What are the main features of the Bohr model of the atom?
- Positively charged central nucleus.
- Electrons (negatively charged) are in discrete energy levels and do not radiate energy
- When an electron makes a transition from one energy level to another a specific amount of energy is lost or gained
- Each line in a spectrum is produced when an electron moves from one energy level to another.
What is a minima?
A point where destructive interference occurs.
How are absorption lines in the Sun produced?
Photons of certain frequencies are absorbed by the gases in the outer atmosphere of the Sun.
What are the advantages of using a grating to produce an interference pattern instead of a double slit?
- Fringes are brighter
- Fringes are sharper
What is a point source?
This is a source where the light spreads evely in all directions
What is the Law of Reflection?
Angle of incidence = Angle of reflection
What is the wavelength of a wave?
Wavelength is the distance from a point on one wave to the same point on the next wave.
What will increase the amount of diffraction?
- Longer wavelengths diffract more
- Narrower gaps cause more diffraction
What is meant by absolute refractive index?
It is the ratio of speed of light in a vacuum to the speed of light in the material.
What is the frequency of a wave?
The number of waves per second.
Using a grating how can you increase the spacing between the maxima?
- Use a grating with a smaller slit separation.
- Use a source with a greater wavelength of light
- Move the screen further away
When is the energy of the ionisation level?
0 Joules
What is constructive intereference?
This occurs when two waves meet at a point in phase.
What is irradiance?
The power per unit area
What is a maxima?
A point where constructive interference occurs.
What type of spectrum is this?
Line absorption spectrum
What is the ionisation level?
This is the energy needed by an electron to leave the atom altogether.
What type of spectrum is this?
Continuous spectrum
A triangular prism can be used to split white light into a spectrum. Why does this occur?
Different frequencies/colours have different refractive indices.
What is the period of a wave?
The time it takes one wave to pass a point.
What is refraction?
The change in speed of light (and wavelength) as it enters a different material, this can result in a change in direction.
What type of spectrum is this?
Line emission spectrum
