ASPhysicsAQAExam Questions3. Waves3.5 Refraction

Refraction (AQA AS Physics)

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3.5 Refraction

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3.5 Refraction

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11 mark

A monochromatic laser beam is shone into a glass tank filled with water. The effects on the laser beam due to the water are observed.

How will the properties of the light be affected by the water?

 

speed

wavelength

frequency

A

no change

increases

decreases

B

decreases

decreases

no change

C

increases

decreases

no change

D

decreases

no change

increases

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    21 mark

    White light is incident on a diamond with a refractive index of 2.61.

    What is the speed of light in the diamond?

    • 0.870 × 108 m s–1

    • 7.83 × 108 m s–1

    • 3.00 × 108 m s–1

    • 1.15 × 108 m s–1

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    31 mark

    Light passing from a vacuum into air undergoes negligible refraction.

    Which response explaining this statement is not correct?

    • Air has a refractive index very close to 1

    • The optical density of air and a vacuum are almost identical

    • Refraction occurs at the boundaries of media with different densities

    • Refraction does not happen when light passes into air

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    41 mark

    A ray of light is incident on a triangular glass block as shown in the diagram below:

    q4_refraction_aqa-as-physics-mcq

    What is the refractive index of the glass?

    • 1.8

    • 0.55

    • 0.45

    • 1.4

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    51 mark

    The following are statements about total internal reflection.

    1.  The critical angle is the angle of incidence when the angle of refraction is 90o
    2. Total internal reflection happens when light passes from a less dense medium into a more dense one
    3. For total internal reflection to occur, the angle of incidence must be greater than the critical angle\
    4. In total internal reflection the angle of incidence equals the angle of reflection

    Which of the statements 1, 2, 3 and 4 are correct?

    • 1, 2 and 3

    • 1, 2 and 4

    • 1, 3 and 4

    • 2, 3 and 4

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    61 mark

    A ray of light is incident on the inside of a glass block at an angle of 65o and reflects internally.

    Which statement is correct?

    • The critical angle for the glass is less than 65o

    • The angle of incidence is less than the critical angle

    • The angle of reflection is 25o

    • The glass block has a refractive index of 1.06

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    71 mark

    Diagrams A, B, C and D show four possible fibre optic cables with their cladding.

    Which is the only correct diagram?

    q7_refraction_aqa-as-physics-mcq

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      81 mark

      What materials are the core of fibre optic cables made from?

      • Copper wires

      • Glass or plastic

      • Very thin aluminium wire

      • Tungsten

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      91 mark

      A pulse of white light passes through an optical fibre and undergoes pulse broadening.

      What would have prevented pulse broadening?

      • Using monochromatic light

      • Using less cladding around the optical fibre

      • Making the white light brighter

      • Using a thicker core

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      101 mark

      Signals can be degraded in optic fibres due to both material and modal dispersion.

      Which of the following would reduce the effect of modal dispersion?

      • Using a narrower core

      • Making the angle of the incident light pulse more acute

      • Having a sheath made from stronger material

      • Using a cladding material with a higher refractive index

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      11 mark

      A ray of monochromatic light is incident on the internal boundary of a rectangular prism, as shown in the diagram.

      Which line shows the correct path for the ray of light?

      You can use the following values:

      • the refractive index of the glass = 1.5
      • the refractive index of air = 1.0
      • the first angle of incidence = 36º

      q11_refraction_aqa-as-physics-mcq

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        21 mark

        Which of the following statements is not correct when total internal reflection occurs?

        • The angle of incidence is greater than the critical angle

        • The light enters a medium with a lower refractive index

        • The light enters an optically denser medium

        • The angles that the incident and reflected rays make with the normal are the same

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        31 mark

        A layer of liquid of refractive index 1.7 covers the horizontal flat surface of a glass block of refractive index 1.6. A ray of light strikes the boundary between them at an angle such that it travels along the boundary afterwards.

        How does the ray strike the boundary?

        • It travels in the liquid at an angle of 70º to the boundary

        • It travels in the liquid at an angle of 20º to the boundary

        • It travels in glass at an angle of 70º to the boundary

        • It travels in glass at an angle of 20º to the boundary

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        41 mark

        Two optical fibres with the same length, and having cores with the same refractive index, but different core diameters are being tested.

        The first fibre, X, has a core diameter which is twice that of the second fibre, Y.

        Rays of light are incident at the same angle θ on the core–cladding boundary of optical fibres X and Y.

        q14_refraction_aqa-as-physics-mcq

        The time for the ray to travel along optical fibre X is

         t space equals space fraction numerator n L over denominator c space sin left parenthesis theta right parenthesis end fraction

        where c is the speed of light in a vacuum.

        What is the time for the ray to travel along optical fibre Y?

        • fraction numerator 4 n L over denominator c space s i n left parenthesis theta right parenthesis end fraction

        • fraction numerator n L over denominator 2 c space s i n left parenthesis theta right parenthesis end fraction

        • fraction numerator 2 n L over denominator 2 c space s i n left parenthesis theta right parenthesis end fraction

        • fraction numerator n L over denominator c space s i n left parenthesis theta right parenthesis end fraction

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        51 mark

        The diagram shows a ray of light travelling in air and incident on a glass block of refractive index 1.25.

        q15_refraction_aqa-as-physics-mcq

        What is the angle of refraction in the glass?

        • 27.3º

        • 40.9º

        • 59.4º

        • 22.5º

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        61 mark

        The diagram shows an optical fibre with a core of refractive index 1.49 and cladding with refractive index 1.47.

        q18_refraction_aqa-as-physics-mcq

        What is the critical angle for monochromatic light travelling in the optical fibre?

        • 42.2o

        • 42.9o

        • 80.6o

        • 81.9o

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        71 mark

        Signals in optical fibres can be distorted due to pulse broadening, particularly when white light is used to transmit the signal. This is because white light contains all the visible wavelengths of light.

        The refractive index of the core for red light is 1.45 and for blue light it is 1.47.

        What is the time difference for pulses of red and blue light to emerge from an optical fibre of length 350 km?

        • 0.23 ns

        • 0.23 μs

        • 6.0 Ms

        • 2.1 Ts

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        11 mark

        A ray of light passes from air, through a layer of oil and through a sheet of glass, as shown in the image below:

         q21_refraction_aqa-as-physics-mcq

        What are the angles of refraction of the light as it enters the oil and then into the glass?

         

        angle refraction in oil / o

        angle refraction in glass/ o

        A

        19.9

        13.0

        B

        19.9

        13.4

        C

        36.1

        35.0

        D

        36.1

        23.0

        You may use the following data:

        • Refractive index of oil n1 = 1.47
        • Refractive index of glass n2 = 1.51

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          21 mark

          A ray of light is incident on a material made from three layers, each having a different optical density, so that in each layer the light travels at a different speed.

          • For layer 1: refractive index = n1 and the speed of light = c1
          • For layer 2: refractive index = n2 and the speed of light = c2
          • For layer 3: refractive index = n3 and the speed of light = c3
          • Angle of incidence = i
          • Angle of refraction = r

          This is illustrated in the diagram below:

          q22_refraction_aqa-as-physics-mcq

          Which is the correct expression for c3, the speed of light in the third layer?

          • fraction numerator c subscript 1 n subscript 1 over denominator n subscript 3 end fraction

          • fraction numerator c subscript 2 n subscript 2 over denominator c subscript 3 end fraction

          • fraction numerator c subscript 1 n subscript 1 over denominator blank n subscript 2 end fraction

          • fraction numerator c subscript 2 n subscript 2 over denominator s i n open parentheses r subscript 3 close parentheses end fraction

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          31 mark

          The speed of light in air is slightly slower than in a vacuum, meaning that as light enters the Earth’s atmosphere from space, it undergoes refraction.

          For an observer standing on Earth, by how much would light from a distant star deviate from a straight line path to their eye?

          Angle of incidence, i = 86.7o

          Refractive index of the upper atmosphere, n = 1.0003

          • 0.30o

          • 3.30o

          • 86.7o

          • 86.4o

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          41 mark

          A step-index fibre has a core with a refractive index 1.50. The cladding has a refractive index of 1.45.

          The diagram below shows light entering the fibre at an angle of 15o.

          q25_refraction_aqa-as-physics-mcq

          The critical angle between the core and the cladding is 75.2o and the optical fibre is 25 km long.

          Which line, A to D in the table below give the minimum and maximum times that pulses of light will take to pass through the fibre?

           

          Minimum time / × 10–5 s

          Maximum time / × 10–5 s

          A

          8.3

          8.6

          B

          12.1

          13.0

          C

          12.5

          8.6

          D

          12.5

          13.0

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            51 mark

            Ultrasound is used in hospitals to produce images of soft tissues. When ultrasound passes from soft tissue into bone it has an increase in speed of 62%.

            If the angle of incidence is 20.0o, what is the angle of refraction?

            • 12.2o

            • 28.2o

            • 33.6o

            • 64.1o

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            61 mark

            Fibre optic cables suffer from signal loss due to absorption caused by attenuation and energy transfers. To counter this effect repeaters are used to amplify the signal.

            If a particular optical fibre loses a constant 1.5 % per kilometre, how much of the original intensity will remain after 20 km if repeaters are not used?

            Assume a constant proportion of the signal is lost every kilometre.

            • 70 %

            • 73 %

            • 74 %

            • 75 %

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            71 mark

            Diamonds are highly valued because of their sparkle. This is caused by total internal reflection, which reflects most of the light that falls onto a cut diamond out of the face we see. Fake gems, called ‘paste’, are often used in jewellery because they are cheaper. However, paste gems sparkle much less than real diamonds.

            The diagrams show a possible path of light through a real diamond, and another through a fake.

            q28_refraction_aqa-as-physics-mcq

            Which row in the table contains only statements which must be true?

             

            critical angle of diamond

             n subscript d over n subscript f

            vd

            A

            Very small

            > 1

            < vf

            B

            Very small

            < 1

            > vf

            C

            Very large

            > 1

            < vf

            D

            Very large

            < 1

            > vf

            Where:

            • n = refractive index;
              • nd is the refractive index of the diamond
              • nf is the refractive index of the fake
            • v = speed of light
              • vd is the speed of light in the diamond
              • v­­f is the speed of light in the fake

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              81 mark

              The graph below shows the refractive index of crown glass for different wavelengths of light.

              q29_refraction_aqa-as-physics-mcq

              If a beam of white light is incident on a prism at an angle of 40o what value will the angle of dispersion of the refracted ray be closest to?

              • 0.07 o

              • 0.71 o

              • 25.14 o

              • 25.07 o

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              91 mark

              Manufacturers can use various methods to test the purity of products.

              If a certain food oil for human consumption has a refractive index of 1.472 when completely pure, how long will it take a beam of light to be detected as it passes through a tank of depth 20 m containing the oil?

              You can ignore the material of the container.

              • 9.81 × 10-9 s

              • 4.53 × 10-8 s

              • 9.81 × 10-8 s

              • 4.53 × 10-6 s

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