A ray of light is incident on a glass slab at angle i. The emergent ray is:
A. Perpendicular to incident ray
B. Parallel to incident ray but laterally displaced
C. Bent towards the normal
D. Bent away from the normal
Answer: Option B
Solution (By JKExamLibrary)
In a parallel-sided glass slab, refraction at first surface bends ray towards normal; at second surface (glass to air), it bends away by equal angle, making emergent ray parallel to incident ray but shifted laterally. No net deviation, only displacement. Memory aid: 'Slab: emergent ray parallel to incident; prism: emergent ray deviated'. This ray optics concept is frequently tested in competitive exams. Always distinguish slab (parallel faces) from prism (non-parallel faces) behavior: slab causes lateral shift, prism causes angular deviation.
Explanation:
Speed = distance/time = 100 m / 5 s = 20 m/s. Convert to km/h: multiply by 18/5 => 20 × 18/5 = 72 km/h. Pole is a point, so train's own length is the distance crossed. Speed in km/h = m/s × (18/5). 20 × 18/5 = 72.
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