In Young's double slit experiment, if the slit separation is doubled and screen distance halved, the fringe width becomes: MCQ with Answer and Explanation
In Young's double slit experiment, if the slit separation is doubled and screen distance halved, the fringe width becomes:
A. One-fourth
B. Double
C. Same
D. Half
Answer: Option A
Solution (By JKExamLibrary)
Fringe width β = λD/d, where λ wavelength, D screen distance, d slit separation. New d' = 2d, new D' = D/2. Thus β' = λ(D/2)/(2d) = λD/(4d) = β/4. Fringe width reduces to one-fourth. Memory tip: 'β ∝ D/d; changes multiply'. This proportional reasoning problem tests wave optics understanding, frequently appearing in competitive exams. Always track how each parameter change affects the result; combine multiplicative factors for net effect. Verify with dimensional analysis: β has length dimension, consistent with λD/d.
Explanation:
Elastic collisions conserve both total momentum and total kinetic energy. Inelastic collisions conserve only momentum. This distinction is fundamental in collision analysis. Memory aid: 'Elastic = KE + momentum conserved; Inelastic = momentum only'. Frequently tested concept to differentiate collision types in competitive exam mechanics sections.
Explanation:
The acceleration due to gravity at a depth 'd' is given by g' = g(1 - d/R), where R is the radius of the Earth. If we go to the center of the Earth, the depth 'd' becomes exactly equal to R. Substituting d = R into the formula gives g' = g(1 - R/R) = g(1 - 1) = 0. So, gravity is zero at the core.
Explanation:
F = BIL sinθ. Maximum when θ = 90° (sin90°=1), so perpendicular. Parallel (θ=0°) force zero. This is the motor effect, used in electric motor.
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