Topic 4.2 Wave Behaviour of Light Flashcards
Define the term monochromatic light
light composed of a single frequency/wavelength with waves that radiate in all directions away from the source.
Define the term ‘coherent wave sources’ and name the three key characteristics
Coherent wave sources are wave sources that maintain a constant wave relationship with each other.
- Approx. same amplitude
- Same frequency
- A constant phase relationship
What is meant by the term ‘in phase’
When two waves are in phase their crest coincide or their troughs coincide
What is meant by the term ‘out of phase’
Two waves are out of phase when one’s crest coincides with the others trough
Explain why light from an incandescent light source is neither coherent nor monochromatic
A incandescent light source uses heat to produce white light.
So firstly, the heat produced is not constant and thus the frequency of the light produced will not be constant.
Secondly, the white light contains many different wave lengths and thus is not monochromatic.
Explain when constructive interference would occur and what observations would be seen.
Constructive interference occurs when waves are in phase. The resultant amplitude is the sum of the individual amplitudes.
For light, we would see an increase in light brightness.
Explain when constructive interference would occur and what observations would be seen.
Destructive interference occurs when waves are out of phase. The resultant amplitude of the wave is the difference between the amplitudes of the individual waves.
For light, we would see a dimming of the light or a dark patch if complete annulment occurred.
Describe the path difference necessary for constructive interference.
The pd of two sources with be m(wavelength) - therefore, a whole number wavelengths from both sources.
Describe the path difference necessary for destructive interference.
The pd of two sources with be (m+1/2)(wavelength) - therefore, half a wavelength more from one sources than the other.
