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NEET-XII-Physics

20: dispersion and Spectra

with Solutions - page 4
Qstn# iv-10-a Prvs-QstnNext-Qstn
  • #10-a
    Find the angle of the second prism. (b) Find the net angular dispersion produced by the combination when a beam of white light passes through it. (c) If the prisms are similarly directed, what will be the deviation in the mean ray? (d) Find the angular dispersion in the situation described in
    (c). (b) Find the net angular dispersion produced by the combination when a beam of white light passes through it. (c) If the prisms are similarly directed, what will be the deviation in the mean ray? (d) Find the angular dispersion in the situation described in
    (c).
    Ans : The deviation of the mean ray is zero.
    Thus, we have:
    δy = (μy - 1)A - (μ'y - 1)A' = 0
    `` \therefore `` (1.60 - 1)A = (1.50 - 1)A'
    ⇒ A = `` \frac{0.50\times 6°}{0.60}=5°``
    (b) Net angular dispersion on passing a beam of white light:
    (μy - 1)ωA - (μy - 1)ω'A'
    ⇒ (1.60 - 1)(0.08)(5°) - (1.50 - 1)(0.07)(6°)
    ⇒ 0.24° - 0.21° = 0.03°
    (c) For the prisms directed similarly, the net deviation in the mean ray is given by
    δy = (μy - 1)A + (μy - 1)A'
    = (1.60 - 1)5° + (1.50 - 1)6°
    = 3° + 3° = 6° (d) For the prisms directed similarly, angular dispersion is given by
    δv - δr = (μy - 1)ωA - (μy - 1)ω'A'
    = 0.24° + 0.21°
    = 0.45°
    Page No 443: (b) Net angular dispersion on passing a beam of white light:
    (μy - 1)ωA - (μy - 1)ω'A'
    ⇒ (1.60 - 1)(0.08)(5°) - (1.50 - 1)(0.07)(6°)
    ⇒ 0.24° - 0.21° = 0.03°
    (c) For the prisms directed similarly, the net deviation in the mean ray is given by
    δy = (μy - 1)A + (μy - 1)A'
    = (1.60 - 1)5° + (1.50 - 1)6°
    = 3° + 3° = 6° (d) For the prisms directed similarly, angular dispersion is given by
    δv - δr = (μy - 1)ωA - (μy - 1)ω'A'
    = 0.24° + 0.21°
    = 0.45°
    Page No 443:
  • #10-b
    Find the net angular dispersion produced by the combination when a beam of white light passes through it.
    Ans : Net angular dispersion on passing a beam of white light:
    (μy - 1)ωA - (μy - 1)ω'A'
    ⇒ (1.60 - 1)(0.08)(5°) - (1.50 - 1)(0.07)(6°)
    ⇒ 0.24° - 0.21° = 0.03°
  • #10-c
    If the prisms are similarly directed, what will be the deviation in the mean ray?
    Ans : For the prisms directed similarly, the net deviation in the mean ray is given by
    δy = (μy - 1)A + (μy - 1)A'
    = (1.60 - 1)5° + (1.50 - 1)6°
    = 3° + 3° = 6°
  • #10-d
    Find the angular dispersion in the situation described in
    (c).
    Ans : For the prisms directed similarly, angular dispersion is given by
    δv - δr = (μy - 1)ωA - (μy - 1)ω'A'
    = 0.24° + 0.21°
    = 0.45°
    Page No 443: