51.

The wavelength of red light from He-Ne laser is 633 nm in air but 474 nm in the aqueous humor inside the eye ball. Then the speed of red light through the aqueous humor is

• 3 × 10⁸ m/s

• 1.34 × 10⁸ m/s

• 2.25 × 10⁸ m/s

• 2.5 × 10⁸ m/s

The radius of curvature of the convex face of a planoconvex lens is 15 cm and the refractive index of the material is 1.4.Then the power of the lens in dioptre is

• 1.6

• 1.66

• 2.6

• 2.66

Magnification at least distance of distinct vision of a simple microscope having its focal length 5 cm is

• 2

• 4

• 5

• 6

The position of final image formed by the given lens combination from the third lens will be at a distance of (f₁ = +10 cm, f₂ = − 10 cm, f₃ = + 30 cm)

• 15 cm

• infinity

• 45 cm

• 30 cm

If the polarizing angle of a piece of glass for green light is 54.7 4°, then the angle of minimum deviation for an equilateral prism made of same glass is [Given : tan 54.74° = 1.414]

• 45°

• 54.74°

• 30°

• 90°

The optical fibres have an inner core of refractive index n₁ and a cladding of refractive index n₂ such that

• n₁ = n₂

• n₁ ≤ n₂

• n₁ < n₂

• n₁ > n₂

A ray of light passes from vacuum into a medium of refractive index, the angle of incidence is found to be twice the angle of refractlon. Then the angle of incidence is

• ${\cos }^{-1} \left(\frac{\mathrm{\mu }}{2}\right)$

• $2 {\cos }^{-1} \left(\frac{\mathrm{\mu }}{2}\right)$

• $2 {\sin }^{-1} \left(\mathrm{\mu }\right)$

• $2 {\sin }^{-1} \left(\frac{\mathrm{\mu }}{2}\right)$

If ε₀ and µ₀ are the electric permittivity and magnetic permeability of free space and ε and µ are the corresponding quantities in the medium, the index of refraction of the medium in terms of above parameter is

• $\frac{\mathrm{\epsilon \mu }}{{\mathrm{\epsilon }}_0{\mathrm{\mu }}_0}$

• ${\left(\frac{\mathrm{\epsilon \mu }}{{\mathrm{\epsilon }}_0{\mathrm{\mu }}_0}\right)}^{1/2}$

• $\left(\frac{{\mathrm{\epsilon }}_0{\mathrm{\mu }}_0}{\mathrm{\epsilon \mu }}\right)$

• ${\left(\frac{{\mathrm{\epsilon }}_0{\mathrm{\mu }}_0}{\mathrm{\epsilon \mu }}\right)}^{1/2}$

A light ray of 5895 $\stackrel{\circ }{\mathrm{A}}$ wavelength travelling in vacuum enters a medium of refractive index 1.5. The speed of light m the medium is

• 3 × 10⁸ m/s

• 2 × 10⁸ m/s

• 1.5 × 10⁸ m/s

• 6 × 10⁸ m/s

The plane faces of two identical plano-convex lenses each having a focal length of 50 cm are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is

• 50 cm

• 25 cm

• 100 cm

• 40 cm