A glass block has a critical angle of 42° - Leaving Cert Physics - Question d - 2015

To determine the refractive index (n) of the glass, we can use the formula relating the critical angle (c) to the refractive index:

$n = \frac{1}{\sin(c)}$

Given the critical angle, c = 42°, we first calculate the sine of the angle:

$\sin(42°) \approx 0.6691$

Now substituting the value into the equation:

$n = \frac{1}{0.6691} \approx 1.493$

Thus, the refractive index of the glass used in the block is approximately 1.493.