CBSE 2022 · Region 3 · Set 2 · Q5 · 3 marks
Monochromatic light of wavelength $\displaystyle 600$ nm is incident from air on a water surface. The refractive index of water is $\displaystyle 1.33$ . Find the (i) wavelength,(ii)frequency and (iii) speed, of reflected and refracted light.
Monochromatic light of wavelength $\displaystyle 600$ nm is incident from air on a water surface. The refractive index of water is $\displaystyle 1.33$ . Find the (i) wavelength,
(ii)
frequency and (iii) speed, of reflected and refracted light.
Marking-scheme solution
(a)
Reflected high
$$\lambda^{\prime}=\lambda=$\displaystyle 600$ \mathrm{~nm} .
$$No change in wavelength
$$c=$\displaystyle 3$ \times $\displaystyle 10$^{$\displaystyle 8$} \mathrm{~m} / \mathrm{s} \text { in air }
$$v=\frac{c}{\lambda}=\frac{$\displaystyle 3$ \times $\displaystyle 10$^{$\displaystyle 8$}}{$\displaystyle 5$ \times $\displaystyle 10$^{$\displaystyle 14$}} \mathrm{~Hz}
$$Refracted light
$$\begin{aligned}
\lambda^{\prime}=\frac{\lambda}{\mu} & =\frac{600}{1.33}=$\displaystyle 451.1$ \mathrm{~nm}
& \simeq $\displaystyle 450$ \mathrm{~nm}
\end{aligned}
$$\begin{aligned}
v= & \frac{c}{\mu}=\frac{$\displaystyle 3$ \times $\displaystyle 10$^{$\displaystyle 8$}}{$\displaystyle 1.33$}
& =$\displaystyle 2.26$ \times $\displaystyle 10$^{$\displaystyle 8$} \mathrm{~m} / \mathrm{s}
& =$\displaystyle 5$ \times $\displaystyle 10$^{$\displaystyle 14$} \mathrm{~Hz}
\end{aligned}
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CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.