Q16DQ - University Physics with Modern Physics

Question

 If we shine white light on an air wedge like that shown in Fig. 35.12, the colours that are weak in the light reflected from any point along the wedge are strong in the light transmitted through the wedge. Explain why this should be so.

Step-by-Step Solution

Answer

The constructive interference which occurred between reflected light from the upper and lower surface of glass explains the strong colours at the transmittance.

Step 1: (a) Concept of interference.

For constructive interference, the condition for path difference $\mathbf{d}$ is,

$\mathrm{d}=\mathrm{m\lambda }$                 $\mathrm{m}=0,\pm 1,=2,...$                             ...(i)

 

For destructive interference, the condition for path difference is,

$\mathrm{d}=\left(\mathrm{m}+\frac{1}{2}\right)\mathrm{\lambda }, \mathrm{m}=0,\pm 1,=2,...$

$\mathrm{d}=\left(\mathrm{m}+\frac{1}{2}\right)\mathrm{\lambda }, \mathrm{m}=0,\pm 1,=2,...$              ...(ii)

Here, $\mathbf{\lambda }$ is the wavelength of light.

Step 2: (b) Explanation of the argument.

The reflection of light happens twice, once at the upper glass surface and once at the bottom glass surface. The constructive peaks are created out of them. Thus, showing strong coloring while they get transmitted through the wedge.