Advertisements
Advertisements
Question
State Snell’s law of refraction of light. Write an expression to relate refractive index of a medium with speed of light in vacuum.
The refractive index of a medium ‘a’ with respect to medium ‘b’ is 2/3 and the refractive index of medium ‘b’ with respect to medium ‘c’ is 4/3. Find the refractive index of medium ‘c’ with respect to medium ‘a’.
Solution
Snell’s law of refraction:
The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This is first law of refraction. Mathematically, it can be given as follows:
`"sin i"/"sin r"=n_(ab)`
Here, nab is the relative refractive index of medium a (incident medium) with respect to medium b (refracted medium).
If the light ray going from vacuum to medium a then the refractive index of medium a can be written as,
`n_a/n_v=n_a` (As nv = 1, for vacuum)
`n_a= "speed of light vacuum"/"speed of light in mediun a"="c"/"v"`
Where, cand v are the speeds of light in vacuum and medium a respectively.
Given:
`n_(ab)=n_a/n_b=2/3`............(i)
`n_bc=n_b/n_c=4/3`...............(ii)
Divide reciprocal of eq. (ii) by eq. (i)
`n_c/n_b÷n_a/n_b=3/4÷2/3`
Thus, `n_c/n_a=9/8 or, n_(ca)=9/8`
APPEARS IN
RELATED QUESTIONS
What is the unit of refractive index?
Which has higher refraction index : water of glass?
Refractive indices of carbon disulphide and ethyl alcohol are 1.63 and 1.36 respectively. Which is optically denser?
What is meant by the refractive index of a substance?
The refractive indexes of four substances P, Q, R and S are 1.77, 1.50, 2.42 and 1.31 respectively. When light travelling in air is incident on these substances at equal angles, the angle of refraction will be the maximum in:
(a) substance P
(b) substance Q
(c) substance R
(d) substance S
The refractive indices of water and glass with respect to air are 4/3 and 3/2 respectively. If the speed of light in glass is 2 × 108ms−1, find the speed of light in (i) air, (ii) water.
_______ is the unit of refractive index.
2n1 : Refractive index of medium 2 with respect to medium 1 : : 1n2 : _______
Match the pair:
| Group 'A' | Group 'B' | |
| Substance | Refractive index | |
| Air | (a) | 1.33 |
| (b) | 1.46 | |
| (c) | 1.0003 |
A light ray enters from medium A to medium B as shown in the figure.
Which one of the two media is denser w.r.t. other medium? Justify your answer.
