Waves 3 Flashcards
(50 cards)
What is required for two-source interference in sound or water waves?
Coherent sources with the same wavelength and frequency
Coherent sources can be achieved by using the same oscillator to drive both sources.
How can two-source interference be demonstrated using light?
Using two coherent light sources or a single laser shining through two slits
This method is known as Young’s double-slit experiment.
What are the characteristics of laser light in the context of Young’s experiment?
Coherent and monochromatic
Monochromatic means there is only one wavelength present.
What is the significance of the size of the slits in Young’s double-slit experiment?
The slits must be about the same size as the wavelength of the laser light to cause diffraction
This allows the light from the slits to act like two coherent point sources.
What type of pattern is produced in Young’s double-slit experiment?
A pattern of light and dark fringes
This pattern results from constructive and destructive interference.
What does a path difference of 0 indicate in Young’s experiment?
Constructive interference resulting in a light fringe
A light fringe occurs when waves reinforce each other.
Who was the first person to conduct the double-slit experiment?
Thomas Young
Young initially used a lamp rather than a laser.
What equation did Thomas Young develop from his experiment?
An equation to calculate the wavelength of light
The formula is related to fringe spacing, slit spacing, and distance from slits to the screen.
How can fringe spacing be measured effectively?
Measure across several fringes and divide by the number of fringe spacings
This method reduces percentage error in the measurement.
What is the formula for fringe spacing in Young’s double-slit experiment?
Fringe spacing (x) = D / a
Where D is the distance from slits to screen and a is the spacing between slits.
What is the implication of a high ratio of D / a in Young’s experiment?
It is needed to make the fringe spacing large enough to see
This is due to the small wavelength of light.
What were the two main theories of light published towards the end of the 17th century?
Newton’s corpuscular theory and Huygens’ wave theory
Newton proposed light was made of particles, while Huygens suggested it was wave-based.
What unique properties of waves could not be explained by Newton’s corpuscular theory?
Diffraction and interference
These properties are crucial to establishing light’s wave nature.
What did Young’s double-slit experiment demonstrate about light?
That light can diffract and interfere
This provided evidence for the wave nature of light.
What happens to interference patterns when you diffract through more slits?
They get sharper, with brighter bands and darker areas in between.
This is due to more beams reinforcing the pattern.
What is the effect of using monochromatic light with a diffraction grating?
The interference pattern is very sharp due to many beams reinforcing the pattern.
Monochromatic light means light of one wavelength.
What is the zero order line in a diffraction pattern?
It is the line of maximum brightness at the center of the pattern.
What are the lines called that are just either side of the central zero order line?
First order lines.
What is the formula to calculate the wavelength of light using a diffraction grating?
d sin θ = nλ.
What does ‘n’ represent in the diffraction grating equation?
The order of maximum being observed.
If the slit separation, d, is larger, what happens to sin θ?
Sin θ is smaller.
What does a larger wavelength do to the diffraction pattern?
It makes the pattern spread out more.
What occurs when white light is diffracted through a grating?
It produces a spectrum with red on the outside and violet on the inside.
Why do astronomers and chemists prefer diffraction gratings over prisms?
They are more accurate for studying spectra.
