Question 1
Refraction of LightA glass plate 0.9 cm thick has a refractive index of 1.50. How long does it take for a pulse of light to pass through the plate? [c = 3.0 × 108 ms−1]
- A.3.0 × 10−11s
- B.4.5 × 10−11s
- C.3.0 × 10−10s
- D.4.5 × 10−13s
Show the answer and explanation
Answer: B (4.5 × 10−11s)
Explanation
Speed of light in glass = c/n = 3.0 × 108 ÷ 1.5 = 2.0 × 108 m s−1. Time = distance ÷ speed = 0.009 m ÷ 2.0 × 108 = 4.5 × 10−11 s.