Institution: বঙ্গবন্ধু শেখ মুজিবুর রহমান বিজ্ঞান ও প্রযুক্তি বিশ্ববিদ্যালয় (BSMRSTU) Exam: A ইউনিট || বঙ্গবন্ধু শেখ মুজিবুর রহমান বিজ্ঞান ও প্রযুক্তি বিশ্ববিদ্যালয় || 2011
Topic: Physics (পদার্থবিদ্যা), Subject: General Science (সাধারণ বিজ্ঞান)

Best Answer Explained in Below-:

To determine the speed of light in glass, we can use the relationship between the refractive index (n) and the speed of light in a medium (v). The refractive index is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in a medium (v):

\[ n = \frac{c}{v} \]

From this formula, we can rearrange it to find the speed of light in a medium:

\[ v = \frac{c}{n} \]

We know the refractive index of water is 1.33 and that of glass is 1.5. The speed of light in a vacuum \(c\) is approximately \(3 \times 10^8 \, \text{m/s}\). However, we will first find the speed of light in water, given as \(2.28 \times 10^8 \, \text{m/s}\).

Using the refractive index of water:

1. The speed of light in water \(v_{\text{water}} = \frac{c}{n_{\text{water}}} \)
2. Knowing that \(v_{\text{water}} = 2.28 \times 10^8 \, \text{m/s}\), we validate this against \(c\).

Next, we find the speed of light in glass using the refractive index of glass:

\[ v_{\text{glass}} = \frac{c}{n_{\text{glass}}} = \frac{3 \times 10^8 \, \text{m/s}}{1.5} = 2.0 \times 10^8 \, \text{m/s} \]

Thus, considering the options given, the correct answer is (A) \(2 \times 10^8 \, \text{m/s}\). This demonstrates that the refraction of light causes it to travel more slowly in materials like glass compared to the vacuum.