waves exam questions Flashcards
The microwaves from the transmitter are polarised. These waves are detected by
the aerial in the microwave receiver (probe). The aerial is a vertical metal rod.
The receiver is moved along the dotted line AE. As it is moved, maximum and
minimum signals are detected. Maximum signals are first detected at points B and
C. The next maximum signal is detected at the position D shown in Figure 5
there is a minima between points C and D because the waves destructively interfere and are out of phase with each other
there is also a path difference for the two waves
The intensity of the waves passing through each slit is the same.
Explain why the minimum intensity between C and D is not zero.
because intensity decreases with distance and one wave travels further than the other wave
The vertical aerial is placed at position B and is rotated slowly through 90° until it
lies along the direction AE.
State and explain the effect on the signal strength as it is rotated.
the waves are polarised and the signal decreases and becomes 0
what if a white colour source is directed at a slit what patterns would be shown
central white fringe
fringes either side showing a range of colour spectrum
A filter transmits only green light of wavelength and red light of wavelength 1.2
This filter is placed between the light source and the single slit.
Describe the interference pattern now seen on the white screen.
Use a calculation to support your answer.
central fringe would be a mixture of red and green light so two waves
spacing of red fringes is 20 percent greater than green fringes
spacing of green fringes is less than of red fringes green fringes are more to the centre
A student decides to use the apparatus shown in Figure 8 to determine the
wavelength of red light using a filter that transmits only red light.
The student suggests the following changes:
* decrease slit separation s
* decrease D, the distance between the slits and the screen.
The student decides to make each change independently.
Discuss the effects each independent change has on the interference pattern, and
whether this change is likely to reduce uncertainty in the determination of the
wavelength.
decreasing slit separation would mean that the waves would diffract more so the fringe on separation would increase uncertainties in measuring fringe separation would decrease meaning uncertainty in measuring wavelength would also decrease
decreasing the distance between the slit and the screen
would mean that diffraction would decrease and the fringe separation would also decrease the uncertainty in measuring wavelength and distance would increase and both of these are needed to measure the wavelength so uncertainty in wavelength would also increase
what use is the core and cladding and how to reduce modal dispersion and material dispersion
core has higher refractive index than cladding
cladding is there to protect the core from damage
reduced material dispersion use monochromatic light
to reduce modal dispersion use core which is narrower
what is superposition
waves traveling in opposite directions meet they have the same speed and same frequency
Explain how a stationary wave is produced when a stretched string is plucked.
they travel to the boundary and are reflected
they tavel in opposite directions and superpose interfering constructively and creating a maximum amplitude
The refractive index of the windscreen glass can vary by a few per cent across the thickness of the glass.
Discuss how this variation may affect the path of the ray through the windscreen
glass.
the change in thickness would not be significant so light may change directions inside windscreen
what is the pattern formed when light enters through single slit
the central maximum is twice as wider than other maxima
central fringe has the highest intensity
intensity decreases with distance from the centre
red filter is used instead of green filter what is the patttern formed
red light has higher wavelength than green light so the fringes would be more spaced out ( maxima further apart) and wider central maxima
In practice, the filter transmits red light with wavelengths in the range 600 nm to
700 nm.
Suggest how this affects the appearance of the maxima.
central maximum unchanged with width
maxima get broader
why amplitude of waves increases and decreases in between points
the waves superpose at some points
when waves are in phase with each other they constructively interfere and a maximum is produced
when waves are out of phase with each other a minimum is produced and the amplitude decreases
what happens when waves travel into a less dense medium
wavelength increase
speed increase
frequency stays the same
and the wave is more spread out
