A LevelPhysicsAQAExam QuestionsWavesInterference

Interference (AQA A Level Physics)

Exam Questions

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11 mark

What is the correct definition for the path difference between two waves?

  • When two waves in phase superimpose to give a wave with a larger amplitude

  • When two waves out of phase superimpose to cancel each other out.

  • The difference in distance travelled by two waves from their sources to the point where they meet.

  • The difference in distance between the source of the two waves.

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21 mark

What is the correct definition for coherent waves?

  • Waves with the same frequency and a constant phase difference.

  • Waves that give constructive interference.

  • Waves travelling at the same speed

  • Waves travelling from the same source

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31 mark

Which experiment can be used to observe the interference of light?

  • Rutherford’s Scattering Experiment

  • Young’s Double Slit Experiment

  • Millikan’s Oil Drop Experiment

  • Herschel’s Discovery of Infrared Radiation

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41 mark

What is the path difference between two waves if they constructively interfere at a point?

  • The difference between the frequency of the two waves

  • The distance between the source of the two waves

  • More information would be needed to calculate this

  • A whole number of wavelengths

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51 mark

Which equipment provides the best source of monochromatic light?

  • The sun

  • A filament lamp

  • A laser

  • A ray box

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61 mark

Which is the correct equation for the fringe separation of light on a screen from Young’s double slit experiment?

  • n lambda equals d space sin left parenthesis theta right parenthesis

  • s i n left parenthesis theta subscript C right parenthesis equals n subscript 1 over n subscript 2

  • W space equals space fraction numerator lambda D over denominator s end fraction

  • n subscript 1 s i n left parenthesis theta subscript 1 right parenthesis equals n subscript 2 s i n left parenthesis theta subscript 2 right parenthesis

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71 mark

When is a bright fringe of light in Young’s double slit experiment formed?

  • When light rays are diffracted through a slit, the bright fringes are formed because of diffraction

  • Two coherent waves of light arrive in phase with each other at a specific point

  • Light from the surroundings constructively interferes with the monochromatic light from the laser on the screen

  • Monochromatic light from the laser gets hot at specific places on the screen

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81 mark

What is the danger of looking directly at a laser beam?

  • It can burn your skin

  • It can make your eye itch

  • It can make you sneeze

  • It can damage your retina

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91 mark

In an experiment similar to Young’s double slit experiment, light from the sun was focused into a narrow beam and shone through two slits. Special cameras were used to view the fringes of each type of radiation.

Which of the following types of electromagnetic radiation would have the greatest fringe separation?

  • Yellow

  • Blue

  • Ultraviolet radiation

  • Infrared radiation

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101 mark

Some students are writing an equipment list needed to carry out Young’s double slit experiment. They know a white screen is needed to clearly see the bright fringes of light.

Which option shows the other equipment needed to carry out Young’s double slit experiment?

A

light bulb

two slits

trundle wheel

B

laser

two slits

vernier callipers

C

laser

single slit

vernier callipers

D

light bulb

single slit

trundle wheel

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    11 mark

    The effect of a double slit on monochromatic light is observed by the set up in the diagram below.

    q11_interference_aqa-as-physics-mcq

    Interference fringes are seen on the screen.

    Which of the following changes would increase the distance between the adjacent fringes?

    • Decrease the width of all the slits

    • Move the screen closer to the double-slit

    • Use light of a higher frequency

    • Decrease the distance between the two slits

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    21 mark

    Certain situations will produce visible interference fringes from two light sources.

    Which of the following conditions will enable visible interference fringes to be seen?

    • Using one light which is polarised at right angles to light from the other source

    • Using incoherent sources

    • Using a red light source

    • Using sources from which the light does not overlap

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    31 mark

    A student sets up an experiment that shows monochromatic light producing interference fringes. The fringes have a separation of w on a screen a distance D away from a pair of slits with separation s.

    The student doubles s and D.

    What would be the new fringe separation?

    • w

    • 4w

    • 2w

    • w over 2

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    41 mark

    A double slit interference experiment is conducted using monochromatic light of wavelength lambda. The centre of the observed pattern is a bright fringe.

    q14_interference_aqa-as-physics-mcq

    What is the path difference between two waves which interfere to give the second dark fringe from the centre?

    • lambda

    • 1.5lambda

    • 2.5lambda

    • 3.5lambda

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    51 mark

    Interference maxima produced by a double source are observed a distance of 2.0 m from the sources. In which one of the following cases are the maxima furthest apart?

    • Red light of wavelength 650 nm from sources 3.5 mm apart

    • Sound waves of wavelength 60 mm from sources 50 mm apart

    • Blue light of wavelength 460 nm from sources 12 mm apart

    • Surface water of wavelength 55 mm from sources 250 mm apart

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    61 mark

    Two wave generators are placed at points S and R to produce sound waves with an identical wavelength. At point T both waves have the same amplitude. The distances from S to T and R to T are shown on the diagram below.

    q16_interference_aqa-as-physics-mcq

    As the student walks from S to T she notices that the volume of the sound increases then decreases repeatedly.

    What is the wavelength of the waves when the wave generators are coherent sources and the amplitude at T is maximum?

    • 10 m

    • 20 m 

    • 5 m 

    • 15 m

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    71 mark

    The diagram is a set–up of the equipment used to investigate the interference of a double slit.

    q17_interference_aqa-as-physics-mcq

    Which of the following changes would increase the fringe spacing?

    • Decreasing the distance w 

    • Decreasing distance x 

    • Decreasing distance y

    • Decreasing the wavelength of the light

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    81 mark

    A student is investigating the interference of waves. They set up coherent waves produced at points S and T and travel outwards in all directions.

    The line XY is halfway between S and T and perpendicular to the joining line S and T. The distance XY is much greater than the distance ST.

    q18_interference_aqa-as-physics-mcq

    Which line or lines would an interference pattern be seen?

    • WZ only

    • XY only

    • Both XY and WZ

    • Neither XY or WZ

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    91 mark

    The diagram shows Young’s double slit experiment performed with a red laser as the light source.

    q11_interference_aqa-as-physics-mcq

    Which option shows how the intensity varies with position for a monochromatic light source on a screen placed after the double slit?

    ms19_interference_aqa-as-physics-mcq

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      101 mark

      A laser illuminates a pair of slits of separation 0.15 mm. The wavelength of light from the laser is 5.5 × 10-7 m. Interference fringes are observed on a screen ten thousand times further away than the size of the slit separation.

      What is the fringe separation as an ordinary number, not in standard form, with the appropriate SI prefix in your units?

      • 5.5 × 10-3 m

      • 5.5 mm

      • 5.5 cm

      • 5.5 × 10-7 m

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      11 mark

      Blue light with a wavelength of 450 nm is used in an experiment to demonstrate interference fringes produced by double-slit interference. The fringe separation is 5.0 mm and the separation of the slits is 0.70 mm.

      What would be the distance between the double slit and the screen?

      • 1.58 × 10-12 m

      • 7.78 m

      • 7.78 × 106 m

      • 7.78 × 10-3 m

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      21 mark

      A Physicist carried out an experiment on Young’s slits using a laser light. The diagram below shows the equipment set up.

      There is also a section of the pattern produced with a ruler placed next to it.

      q22_interference_aqa-as-physics-mcq

      What is the wavelength of the light?

      • 30 nm

      • 3 nm

      • 0.03 nm

      • 3 × 10-4 m

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      31 mark

      In a Young’s double-slit experiment, the spacing of the double slits is s and the distance between the slits and the screen on which fringes are formed is D. When monochromatic light of wavelength λ is incident on the slits the distance between adjacent fringes on the screen is w.

      Which row shows another arrangement that produces a fringe spacing of w?

       

      Wavelength of the light

      Distance between the slits and the screen

      Spacing of double Slits

      A

      4 lambda

      2D

      4s

      B

      2 lambda

      2D

      2s

      C

      4 lambda

      2D

      2s

      D

      4 lambda

      2D

      8s

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        41 mark

        In the diagram, K is the source of a wave of frequency 25 Hz.

        q24_interference_aqa-as-physics-mcq

        The wave travels to M by two routes, K → L → M and K → M. The speed of the wave is 15 m s-1.

        What is the path difference between the two waves at M in terms of the wavelength λ of the waves?

        • 4 lambda

        • 6.6 lambda

        • 31.6 lambda

        • 2.4 lambda

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        51 mark

        The diagram below shows an arrangement used to investigate double slit interference using microwaves.

        q25_interference_aqa-as-physics-mcq

        The diagram below shows the view from above.

        q25-2_interference_aqa-as-physics-mcq

        The microwaves from the transmitter are polarised. These waves are detected by the aerial in the microwave detector (probe). The aerial is a vertical metal rod.

        The detector is moved along the dotted line UY. As it is moved, maximum and minimum signals are detected. Maximum signals are first detected at points V and W. The next maximum signal is detected at the position X.

        The distances between each of the two slits, S1 and S2 and the microwave receiver when the aerial is in position X are S1X = 0.3335 m and S2X = 0.3615 m

         Select the three correct reasons that explain why the signal strength falls to a minimum between U and V, and between V and W.

         

        Reason 1

        Reason 2

        Reason 3

        A

        Waves are out of phase

        Creating the path difference

        Constructive interference occurs

        B

        Waves are out of phase

        Creating the path difference

        Destructive interference occurs

        C

        Waves have a path difference

        Path difference is a half-integer number of wavelengths

        Destructive interference occurs

        D

        Waves have a path difference

        Path difference is a half-integer number of wavelengths

        Constructive interference occurs

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          61 mark

          A sound source X1 is positioned w cm to the left of sound source X2. Both sound sources are y m below the detection line AB. AB runs parallel to X1X2 . When a sound detector is slowly moved along the line AB, a maxima is first detected at P, followed by a minima at Q, with another maxima at R and a minima at S. PQRS are all equidistant apart with X1 S = X2 S.

           Which one of the following is a correct expression for the wavelength of the sound?

          • X1Q - X1P

          • X1R - X1Q

          • X1Q - X2Q

          • X1R - X2R

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          71 mark

          The diagram shows the paths of microwaves from two narrow slits, acting as coherent sources, through a vacuum to a detector.

          q27_interference_aqa-as-physics-mcq

          The frequency of the microwaves is 8.7 GHz.

          Calculate the value of the path difference of the two waves arriving at the detector.

          • 2λ

          • 0.069 m

          • 6.9 × 107 m

          • 0.0345 m

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          81 mark

          The screen below shows the maxima of a two slit interference pattern produced on a screen when a laser was used as a monochromatic light source.

          q28_interference_aqa-as-physics-mcq

          The slit spacing is 0.45 mm.

          The distance from the slits to the screen = 9.6 m.

          Use the diagram above to calculate the wavelength of the light that produced the pattern.

          • 7.0 × 10-7 m

          • 70 nm

          • 5.63 × 10-6 m

          • 7.97 × 10-7 m

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          91 mark

          White light is passed through a double slit and an interference pattern is observed on a screen 2.1 m away. The separation between the slits is 0.6 mm. The first violet and red fringes are formed 1.8 mm and 3.3 mm respectively away from the central white fringe.

          What are the wavelengths of the violet and red light?

          • Violet light wavelength = 0.94 m and red light wavelength = 0.51 m

          • Violet light wavelength = 2570 nm and red light wavelength = 514 nm

          • Red light wavelength = 943 nm and violet light wavelength = 514 nm

          • Violet light wavelength = 943 nm and red light wavelength = 514 nm

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          101 mark

          Green light with a wavelength of 550 nm is used in an experiment to show interference fringes produced by double-slit interference. The fringe separation is 3.5 mm and the separation of the slits is 0.70 mm.

          What would be the distance between the double slit and the screen?

          • 4 450 000 m

          • 4.45 m

          • 1.1 × 10–7 m

          • 4.45 × 10–9 m

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