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9. Ray optics abd optical instruments — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics9. Ray optics abd optical instruments1 Mark
MCQ
Electromagnetic waves emanating from a point $A$ (in air) are incident on a rectangular block of material $M$ and emerge from the other side as shown below. The angles $i$ and $r$ are angles of incidence and refraction when the wave travels from air to the medium. Such paths for the rays are possible,
  • A
    if the material has a refractive index very nearly equal to zero
  • B
    only with gamma rays with a wavelength smaller than the atomic nuclei of the material
  • ✓
    if the material has a refractive index less than zero
  • D
    only if the wave travels in $M$ with a speed faster than the speed of light in vacuum
✓

Answer

Correct option: C.
if the material has a refractive index less than zero
c
(c)

In given case, angle of refraction is negative. 'This is possible only when refractive index of matcrial is negative. Negative Index Metamaterial $(NIM)$ is a material for which refractive index has a negative value for an electromagnetic wave over certain frequency range. 'These are artificially produced materials, which found their application in optical signal transmission.

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