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What is the strength of transverse magnetic field required to bend all the photoelectrons within a circle of a radius 50 cm when light of wavelength 3800 A ∘ is incident on a barium emitter? (Given that work function of barium is 2 .5 eV ; h = 6 .63 × 10 - 34 J s ; e = 1.6 × 10 - 19 C ; m = 9.1 × 10 - 31 kg )

Options

  1. A4 .88 × 10 - 4   T
  2. B32 × 10 - 5   T
  3. C6.32 × 10 - 6   T
  4. D7 .6 × 10 - 8   T

Correct answer

C. 6.32 × 10 - 6   T

Step-by-step solution

1 2 m v m a x 2 = h c λ - ϕ 0 or v m a x 2 = 2 m h c λ - ϕ 0 = 2 9.1 × 10 - 31 × 6.63 × 10 - 34 × 3 × 10 8 3.8 × 10 - 7 - 2.5 × 1.6 × 10 - 19 = 27.12 × 10 10 m 2 s - 2 Now, B = m v m a x e R m a x = 9.1 × 10 - 31 × 5.21 × 10 5 1.6 × 10 - 19 × 0.5 = 6.32 × 10 - 6 T

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