NEET · Physics · STD 12 - 9. Ray optics and optical instruments
A beam of light from a source \(L\) is incident normally on a plane mirror fixed at a certain distance \(x\) from the source. The beam is reflected back as a spot on a scale placed just above the source \(L.\) When the mirror is rotated through a small angle \(\theta\), the spot of the light is found to move through a distance \(y\) on the scale. The angle \(\theta\) is given by
- A \(\frac{y}{x}\)
- B \(\;\frac{x}{{2y}}\)
- C \(\;\frac{x}{y}\)
- D \(\;\frac{y}{{2x}}\)
Answer & Solution
Correct Answer
(D) \(\;\frac{y}{{2x}}\)
Step-by-step Solution
Detailed explanation
When mirror is rotated by \(\theta\) angle reflected ray will be rotated by \(2 \theta .\) For small angle \(\theta\) \(\quad \tan 2 \theta \approx 2 \theta=\frac{y}{x}\)
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