Answer:
b) the refracted ray has an angle of 90 degrees
Explanation:
The angle of incidence is measured with respect to the normal separation of the media. The critical angle for total internal reflection occurs is:

Here
and
are the refractive index of the mediums. This equation is an application of Snell's law, for the case where the refracted ray has an angle of
.
Answer:
The focal length of a lens is refers to the distance from the center of the lens to the principal foci.
Answer:
The intensity of sound (I) = 3.16 x 10⁻⁶ W/m²
Explanation:
We have expression for sound intensity level (SIL),

Here we need to find the intensity of sound (I).

Substituting
L = 67 dB and I₀ = 10⁻¹² W/m² in the equation

The intensity of sound (I) = 3.16 x 10⁻⁶ W/m²