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  9. Q67

UKPSC PCS 2024 · Question 67 of 142

Two slits are made one millimetre apart and the screen is placed one metre away. What is the fringe separation when blue-green light of wavelength 500 nm is used ?

Science & Tech

  1. A0.5 m
  2. B0.5 mmCorrect
  3. C50 mm
  4. D50 m

Answer: B. 0.5 mm

Explanation

Fringe width = lambda*D/d = 500 nm x 1 m / 1 mm = 0.5 mm.

Source: UKPSC Combined Upper PCS Prelims GS Paper-I, Series-A, held 14 Jul 2024 (teachingninja PDF); answer from official UKPSC Series-A key

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