Question

Two transparent slabs have the same thickness as shown in Fig. One is made of material A of refractive index. 1.5. The other is made of two materials B and C having thickness in ratio 1 : 2, the refractive index of C is 1.6. If a monochromatic parallel beam passing through the slabs has the same number of wavelengths inside both, the refractive index of B is –

• A. 1.1
• B. 1.2
• C. 1.3
• D. 1.4

Answer 1

Answer: (C)

1.3

Answer 2

No. of wavelength are same

so optical path length will be same

µ_Ax_A = µ_B x_B + µ_Cx_C

(1.5) t = µ_B $\left( \frac { \mathrm { t } } { 3 } \right)$ + (1.6)

4.5 = µ_B + 3.2 Ž µ_B = 1.3