Which one of the following phenomena is not explained by Huygens' construction of wavefront?

A parallel beam of monochromatic light is incident on a glass slab at an angle of incidence $45^{\circ} .$ Find the ratio of width of beam in air to that in glass (If refractive index of glass is $1.5$).

On a hot summer night, the refractive index of air is the smallest near the ground and increases with a height from the ground. When á light beam is directed horizontally, the Huygens' principle leads us to conclude that as it travels, the light beam

A parallel beam of monochromatic light is incident on a glass slab at an angle of $35^{\circ} .$ The ratio of width of beam in glass to that in air is$\left[{\mu }_{\mathrm{g}}=1.5\right]$

For passage of monochromatic beam of light in a medium of refractive index $1.5$, the plane wavefront makes an angle of$60°$  with the refracting surface. The ratio of the width of beam in medium to that in air is

Velocity of light in diamond is $\left(\frac{2}{5}\right)^{\text {th }}$ that in air. Velocity of light in water is $\left(\frac{3}{4}\right)^{\mathrm{th}}$ that in air. The angle of incidence of a ray of light travelling from water to diamond $\left(r=30^{\circ}\right)$ is

When a plane wavefront is incident on a double convex lens, the refracted wavefront is