The critical angle for a medium of refractive index 1.5 is closest to
Correct answer: B. 42 degrees
- A. 30 degrees
- B. 42 degrees
- C. 60 degrees
- D. 90 degrees
Explanation
The sine of the critical angle equals one over the refractive index, so sin C is 0.667 and C is about 42 degrees, the standard value for ordinary glass. A higher refractive index gives a smaller critical angle, which is why diamond at 2.42 has a critical angle of only 24 degrees and traps light so effectively. Water, at 1.33, gives about 49 degrees.
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About Optics
Light is studied through reflection, refraction, dispersion, interference, diffraction and polarization, linking ray behavior with its wave nature. Questions may involve mirrors, lenses, optical instruments, refractive index and image formation, while geometrical optics deals with rays and wave optics explains effects such as interference and diffraction.
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