Understanding Waves: Questions on Phase Differences and Interference Patterns

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In summary, the first conversation discusses two sources emitting long-range radio waves with a phase difference of 90°, and a detector at a greater distance from A than B by 82 m. The second conversation is about a double-slit experiment with two interference patterns visible on the screen due to light of different wavelengths. The question asks for the separation between the m = 4 bright fringes of the interference patterns.
  • #1
WesleyHuang
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1.
Sources A and B emit long-range radio waves of wavelength 320 m, with the phase of the emission from A ahead of that from source B by 90°. The distance rA from A to a detector is greater than the corresponding distance rB from B by 82 m. What is the magnitude of the phase difference at the detector?


2.
In a double-slit experiment the distance between slits is 5.2 mm and the slits are 0.82 m from the screen. Two interference patterns can be seen on the screen: one due to light of wavelength 450 nm, and the other due to light of wavelength 580 nm. What is the separation in meters on the screen between the m = 4 bright fringes of the two interference patterns?



The first one is actually an online-test question. I have tried 3 times using the method from the textbook, but i still haven't got the right answer. Can anyone help me? THANKS!
 
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  • #2
You understand, don't you, that you have to show what you have done yourself?
 
  • #3
HallsofIvy said:
You understand, don't you, that you have to show what you have done yourself?

Hello! What i have done for the first question is:
devide the wave length 320m by 4, since A is 90° ahead (a quarter of a cycle)
then I take 82m away from it, since the wave from source A goes 82m further
finally i just take the ratio of the phase difference with the wavelength and multiply the result by 2π in order to convert the unit to radian.

is it correct?
 
  • #4
i can't do the second one. i thought the 2 lights will not have any bright fringes, because the wavelengths are different, double-slit interference will not occur...
do you think so?
 
  • #5
Tips:
1. How much is A in front of B? (90 deg)
How big is the phase difference between A and B just because wave A has to travel longer?

2. For both 450 nm and 580 nm a double-slit interference will occur. What distance for m=4 at 450 nm and what distance for the 580 nm wave?
 
  • #6
I've got the answers now! thanks!
 

1. What are waves?

Waves are disturbances that transfer energy from one place to another without transferring matter.

2. What are the different types of waves?

There are two main types of waves: transverse waves and longitudinal waves. Transverse waves have vibrations perpendicular to the direction of energy transfer, while longitudinal waves have vibrations parallel to the direction of energy transfer.

3. How do waves form?

Waves are formed when a source of energy causes a disturbance in a medium, such as air or water. This disturbance creates a ripple effect, causing the energy to transfer from one point to another.

4. What is the difference between amplitude and wavelength?

Amplitude refers to the maximum displacement of a wave from its resting position, while wavelength is the distance between two consecutive points of the same phase on a wave. In simpler terms, amplitude is the height of a wave and wavelength is the length of one complete wave cycle.

5. How do waves interact with each other?

When two waves meet, they can either interfere constructively or destructively. Constructive interference occurs when the peaks of two waves align, resulting in a larger wave, while destructive interference occurs when the peaks of one wave align with the troughs of another, resulting in a smaller wave or cancellation of the wave altogether.

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