In the figure, a light initially in material $1$ refracts into material $2,$ crosses that material and is then incident at the critical angle on the interface between materials $2$ and $3.$ The indexes of refraction are $n_1=1.80, n_2=1.40$ and $n_3=1.20$
(a) What is angle $\text{θ}?$
(b) If $\text{θ}$ is increased, is there refraction of light into material $3?$

A plane electromagnetic wave with wavelength $5.0 \mathrm{m}$ travels in vacuum in the positive direction of an $x$-axis. The electric field of amplitude $215 \mathrm{V} \mathrm{m}$ oscillates parallel to the $y$-axis. What are the (a) frequency, (b) angular frequency, and (c) angular wave number of the wave?
(d) What is the amplitude of the magnetic field component?

(e) Parallel to which axis does the magnetic field oscillate?

(f) What is the time-averaged rate of energy flow in watts per square meter associated with this wave? The wave uniformly illuminates a surface of area $2.0 {\mathrm{m}}^2.$ If the surface totally absorbs the wave, what are (g) the rate at which momentum is transferred to the surface and (h) the radiation pressure on the surface?

Figure depicts a simplistic optical fiber: a plastic core $\left(n_1=1.58\right)$ is surrounded by a plastic sheath $\left(n_2=1.46\right).$ A light ray is incident on one end of the fiber at angle $\text{θ}.$ The ray is to undergo total internal reflection at point $A,$ where it encounters the core-sheath boundary. (Thus there is no loss of light through that boundary.) What is the maximum value of $\text{θ}$ that allows total internal reflection at $A?$