18. For the design of symmetric dielectric slab waveguides, given the conditions(i) smaller refractive index contrast (ii) thicker core layer (iii) higher operation frequency, how many conditions above will let the waveguide more likely to be single-moded? (A) 1 (B) 2 (C) 3 (D) none of the above

8. The plates of a parallel-plate capacitor has areas of 10 cm² each and are separated by 1 cm. The capacitor is filled with a dielectric material with ε = 4ε₀, where ε₀ = 8.85 × 10⁻¹² F/m, and the voltage across it is given by V(t) = 30cos(2π×10⁶t) (V). What is the displacement current? (A) Id = 2.4πε₀ × 10⁷sin(2π × 10⁷t) ( A ) (B) Id = 2.4πε₀ × 10⁹cos(2π × 10⁷t) ( A ) (C) Id = 2.4πε₀ × 10⁹sin(2π × 10⁷t) ( A ) (D) None of the above.

18. For the design of symmetric dielectric slab waveguides, given the conditions
(i) smaller refractive index contrast (ii) thicker core layer (iii) higher operation frequency, how many conditions above will let the waveguide more likely to be single-moded?
(A) 1
(B) 2
(C) 3
(D) none of the above

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