8.3. Interference
A subsection of Physics, 9702, through 8. Superposition
Listing 10 of 90 questions
By reference to the direction of propagation of energy, state what is meant by a longitudinal wave. State the principle of superposition. The wavelength of light from a laser is determined using the apparatus shown in . double slit screen light 2.3 m 3.7 × 10–4 m (not to scale) The light from the laser is incident normally on the plane of the double slit. The separation of the two slits is 3.7 × 10–4 m. The screen is parallel to the plane of the double slit. The distance between the screen and the double slit is 2.3 m. A pattern of bright fringes and dark fringes is seen on the screen. The separation of adjacent bright fringes on the screen is 4.3 × 10–3 m. Calculate the wavelength, in nm, of the light. wavelength = nm The intensity of the light passing through each slit was initially the same. The intensity of the light through one of the slits is now reduced. Compare the appearance of the fringes before and after the change of intensity.
9702_s20_qp_21
THEORY
2020
Paper 2, Variant 1
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State the principle of superposition. Two waves, with intensities I and 4I, superpose. The waves have the same frequency. Determine, in terms of I, the maximum possible intensity of the resulting wave. maximum intensity = I Coherent light of wavelength 550 nm is incident normally on a double slit of slit separation 0.35 mm. A series of bright and dark fringes forms on a screen placed a distance of 1.2 m from the double slit, as shown in . The screen is parallel to the double slit. 0.35 mm double slit light wavelength 550 nm screen 1.2 m (not to scale) Determine the distance between the centres of adjacent bright fringes on the screen. distance = m The light of wavelength 550 nm is replaced with red light of a single frequency. State and explain the change, if any, in the distance between the centres of adjacent bright fringes.
9702_s21_qp_23
THEORY
2021
Paper 2, Variant 3
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State the principle of superposition. Coherent light of wavelength 590 nm is incident normally on a double slit, as shown in . screen P 2.6 m 1.4 mm A B coherent light wavelength 590 nm double slit (not to scale) The separation of the slits A and B is 1.4 mm. Interference fringes are observed on a screen placed parallel to the plane of the double slit. The distance between the screen and the double slit is 2.6 m. At point P on the screen, the path difference is zero for light arriving at P from the slits A and B. Determine the separation of bright fringes on the screen near to point P. separation = mm The variation with time of the displacement x of the light wave arriving at point P on the screen from slit A and from slit B is shown in a and b respectively. x / arbitrary units –3 –2 –1 time wave from slit A a x / arbitrary units –2 –1 time wave from slit B b 1. State the phase difference between waves forming the dark fringe on the screen that is next to point P. phase difference = ° 2. Determine the ratio intensity of light at a bright fringe intensity of light at a dark fringe . ratio =
9702_w10_qp_23
THEORY
2010
Paper 2, Variant 3
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Questions Discovered
90