Discussion
A ray of light enters two media X and Y having different optical densities. Refer to the table given below and identify A, B, C and D :
| Medium | Change in speed of light | Change in frequency of light | Change in wavelength of light |
|---|---|---|---|
| X | Increases | A | B |
| Y | C | D | Decreases |
Answer: C
The answer is A-No change; B-Increases; C-Decreases; D-No change.
When light passes from one medium into another, its frequency is fixed by the source and does not change. Speed and wavelength change together, since
\[ \begin{aligned} v &= f\lambda \\ \lambda &\propto v \ \text{when } f \text{ is fixed} \end{aligned} \]
In X the speed increases, so frequency shows no change (A) and wavelength increases (B). In Y the wavelength decreases, so the speed decreases (C) and the frequency again shows no change (D). Options A and D let frequency change, and option B has the wavelength falling while speed rises.
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