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Light – Reflection and Refraction — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceLight – Reflection and Refraction4 Marks
Question
When light ray goes from one transparent medium to another transparent medium, it suffers a change in direction, into second medium. The extent of the change in direction suffered by the phenomenon of change in the path of light rays when going from one medium to another medium is known as refraction. Ray is a given pair of media can be expressed in terms of refractive index. The refractive index is related to an important physical quantity in the relative speed of light in different media.

(i) A ray of light enters into the glass from air. Does it bend towards normal ?
(ii) What is the unit of refractive index?
(iii) Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is $3 \times 10^3 ms ^{-1}$.
or
(iii) When light goes from one medium to another, which of the three parameters, frequency, wavelength, velocity change?
✓

Answer

(i) Yes, it bends towards normal.
(ii) No unit.
\[n_m=\frac{\text { Speed of light in vacuum }}{\text { Speed of light in the medium }}=\frac{c}{v}\]
Speed of light in vacuum,
\[c=3 \times 10^8 ms ^{-1}\]
Refractive index of glass,
\[n_s=1.50\]
Speed of light in the glass,
\[\begin{aligned}v & =\frac{c}{n_g} \\& =\frac{3 \times 10^8}{1.50}=2 \times 10^8 ms ^{-1}\end{aligned}\]

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